So, just what exactly is the nature of the travellers AND what exactly is their nature towards the otherside...
What will be interesting going forward is to find out why exactly the travellers even care about this object; why it isn't just Tessa's pet revenge project--when it is clearly MUCH MORE than just that!? I think that "the otherside" is where "the spirits" (who may very well be "the travellers" over there, basically Gods over all other supernatural creatures; their own heaven or fabricated paradise...) control the witches and even magic to some degree via it.
They control magic by telling witches (who, when they die, are now forced without choice to go to this purgatory of sorts--who knows what in the hell they can do to you there...if they were the ones that causeed Grannie "pain", then they indeed have quite a bit of power over there) how their relatives, their ancestors and bloodline should "practice" magic. The "key" to this process is that they use a magical process that is "controlled" and manipulated via their ancestors on the otherside--the real issue is to make sure they NEVER find out that expression is the real "magic", the real unfiltered, unbound, and free magic that witches should use (but it should be true as Grannie as said, that expression is quite a bit more dangerous to use--if you don't know what you are doing--the magic Grannie taught Bonnie is magic with it's mouth and claws de-fanged and also less prone to "accidents"; a perpetual magic that has safety wheels attached). They learn what the "good" way is and what the "wrong" way is to use magic. This may be why Bonnie has been getting threatened, along with her grandmother--getting "tortured" or something akin to this--because Bonnie has learned what REAL magic is (thanks to Silas): expression.
The original "spirit" based magic that Bonnie started with and had been using (plus the "evil magic" with the potential "evil spirits", but again that was another magic that "the spirits" didn't want her to use, so who knows what the truth to that magic is), along with Davina's "ancestry" magic were and are both frauds that only allow you to use a VERY diminished version of true magic. It seems to me that all forms of magic that we know of so far are being "channeled" and then allowed to be used by witches, but the foundation upon which it all TRULY stands upon is: expression (which Silas taught to Bonnie, most likely in spite of "the travellers AND Tessa", plus it is his "Ace" just in case he himself cannot get rif of the otherside or save himself--Bonnie is his true backup plan I think). When Bonnie wanted to ressurect Jeremy the first time it required the energy of hundreds of whiches, yet the second time with expression it required far less (though Bonnie didn't have very good control of it yet. as she died)...
We've seen that expression is by far a more potent magic than any other kind and as I said, I think the travellers via the otherside are channeling ALL magic through there and creating "secondary" types of magic to manipulate all witches and to make them--by far--the most powerful witches. Making them, the possible "Original Witches". But, it may be that there are witches even stronger (or "beings"), these "witches" would be "the spirits" (with those that are good, manipulative, and also evil--as Grannie seemed to sense and also get attacked by something like that when Bonnie used a certain spell...) that seem to control everything from the otherside (though if the otherside is brought down, just what exactly is going to happen--maybe those daggers that the travellers have are akin to the anchor, but in reverse; that way when it IS brought down, just as Tessa "magically" somehow slipped back into our world without a spell, perhaps all of the travellers will come back as well if their dagger remains...unharmed--this may also mean other beings may come back or "slip" through the cracks as the veil of the otherside is fully lifted and it is destroyed...).
I imagine the rest of this season will be centered on Bonnie and Jeremy, with the Augustine vampire and Katherine's issues being the rest (plus Matt, we can't forget about him...). Jeremy and Bonnie are both facing potentially huge ramifications from what is going on: Bonnie being a ghost that exists DUE to "the otherside", yet being the anchor that allows it to even exist--akin to a paradox, a chicken and the egg issue if you will... Then Jeremy is a ressurected hunter. The issue with him is: Jeremy is a hunter with the main objective of killing Silas (which is now DONE)--how will this affect him? Second, when he was ressurected there was a price to be paid (as the witches mentioned; or was it the spirits?). This price turned him into a medium, but we don't understand the nature of this ability or the price paid... So far it looks to be a price that was "in his favor" (making you wonder, why was it a "price" or at least called one...). Could this mean that if the otherside is brought down, not only will Jeremy not see ghosts anymore, but could something far worse happen since he may have a link to "the otherside" that is a little unknown.
Much how Bonnie has one foot on the otherside and due to the anchor she has one foot here--allowing her to exist. May Jeremy be the same, but in reverese? He has one foot here (from the ressurection), but also one foot on the otherside (allowing him to see ghosts and to come back to life more easily...). If that is true, for both Bonnie and Jeremy, taking down the otherside without a properly adressing these issues, may mean they will both perish...?
There are a lot of things that have to be explained in this. There is a lot of this that may be wrong, I won't deny that at all--this is after all just a stab in the dark. But, it makes sense that The Travellers are clearly doing something big and it has to do with the otherside. I'm sure that at some point The Travellers will come to do something with Bonnie (take her away, or at least stay around her en masse, to guard her). Those daggers most certainly do something interesting, though we do not know what yet.
IF, The Travellers have anything to do with the way witches and magic are being controlled--mostly information wise (as even Esther didn't know what expression was, which tells me that even though she is "technically" dead and the anchor...Bonnie has a HUGE role to play, because she knows how to TRULY use magic)--and how the otherside is being used...the spirits... Then things will get interesting. Even IF "the spirits" end up being the true "Original Witches" or entirely different supernatural beings that are extremely powerful, but still were or are on the otherside; I imagine that when the otherside is being brought down (or is brought down) they will show up. Using the method Tessa did to ressurect themselves (as I mentioned earlier).
I said what the rest of this season will be about, but next season will be all about the ramifications: the otherside and what comes out of it (or if things get really bad, what goes INTO it...). With the possibility of an all-out-war with The Travellers (who I imagine will be unhappy).
The scooby-gang does need to realize at somepoint however that the otherside needs to be obliterated. It isn't right that peoples loved ones are kept from each other, especially when they are being used, manipulated, and lorded over by the creators of this "paradise prison". All people, supernatural or otherwise need to be sent to the same afterlife that humans are afforded...