So, at the very end of the season finale of season 4, Silas tells Stefan that "Nature has a loop hole, when a witch dies, her spell becomes undone." Silas was stone for 2 thousand years, because Qetsiyah cast a spell that made him that way. (just like Bonnie did.) If nature does have that loop hole, then wouldn't Silas have became unstoned, because she "died." That gets your mind wondering, "How did he stay stone for 2,000 years?"
Qetisyah and Silas created the immortaility spell, so even though Qetisyah didnt become immortal right away, couldn't she have become immortal right before she died? If she is really the most powerful witvch ever, she should have figured out a way to become immortal and still stay a witch.
Qetisyah created the other side so Silas could take the cure and spend enternity there with her. Now, Qetisyah created the other side, so shoudln't she be able to traavel back and forth freely. Remeber when Silas told Bonnie that Qetisyah wouldn't be contacting her any time soon. Would that be because she was on Earth? But, she found Voughn and reminded him of his destiny. If she died 1,900 years ago, wouldn't Silas have become unstone? Qetisyah is not dead, she is immortal and still a witch and can travel to the other side and back to Earth because she created the other side.