For new players coming through, it makes a lot more sense to force completion of CT at the point in the story when it's supposed to happen, i.e. shortly after the events at the Praetorium with Nero "newly unemployed" and still sore from his defeat there, and prior to his reappearance in post-Heavensward.

For anyone already past that point, there'll also have to be a second gate prior to 5.3 that no new player is going to hit.