the prevailing theory that I see popping up everywhere is that his Bankai is going to include his hollow form in some way. I'm sure we all remember the fanart that was floating around at the start of this arc, well people seem to think his Bankai will be something along those lines, a 1/2 way point between his old bankai and his Full Hollow form he used against Ulquiorra.
It makes sense, as he now acknowledges and accepts his hollow form, along with understanding that his REAL powers come directly from them. So it would fit that now he's accepted it all, he can access the power and control it.