We are getting (at least) one more GCD, the "Eventide" kind of attack that happens after Living Shadow is summoned. Personally I would not want DRK to gain a lot more GCD's because being ogcd heavy is the only thing making it not feel the same as playing Warrior right now. I'd also not like more sustain, having good mitigation and less sustain makes Dark Knight fun. Health is for Paladins and Warriors, we're supposed to summoning the darkness here.

There could be some cool stuff we don't know about yet, But can't count on too much; Yoshida stated "8.0" would be when tanks gain greater individuality. I'm not sure why the wait for that is so long, but that's when it's happening. For the next three years Dark Knight will be about good as what the balance patch determines for damage per second.