I think in the long run there will be more 767's but it may not be for a long while yet. If the bar is used for 321's 757's as well as the 767 it makes sense to buy one that can operate all three. Therefore you can accept larger diverts etc, I don't think they would have bought it just on the chance of more immenant 76's.
CO76 - 146 PAX CO77 - 176 PAX today not sure where the extra 4 sat!!!