The trick is though is that we were supposed to start with CT, and once it's implemented, that's how anyone who hasn't reached that point in the game yet will progress, with CT first in order to gear up for BC instead of having to rely soley on myth grinding. BC isn't going to be the next step, because CT IS first, then BC, so it will be CT again. It will appear as though CT gets two patches in a row, but only because the first one is due to the dungeon having been postponed to be worked on.
It was meant to be there at launch; its inclusion in patch 2.1 isn't an addition, it's SE completing a link of the end game chain that's been missing since day 1. Not sure if that last available turn in the coil is still bugged at the end, but I would wager that that bug being fixed is the only new thing we'd see in BC before CT gets its next level in 2.2, or 2.3, or whatever.