At the moment the 767 is scheduled to operate until about June time 2016 then the 777 4 class aircraft is taking over ( pencilled in at the moment but could change )
There is a demand again for first class into Nassau and obviously an upgraded experience for the other cabins as well !
The 787 9 series is also a possible choice but the ground engineers in Nassau have been trained up on the 777 recently
The airport at Nassau is quite capable of handling the 747 as has been used quite recently on a weather diversion from Miami and Grand Cayman can also handle a 777 as again BA operated direct to LGW many years ago when AML operated the route on behalf of BA