In the BA investors website , it states that the remaining 10 Ex B-CAL A320's will start to disperse nov 07 - dec 08.
To be replaced by 7 x A321 and 3 x A320
Everybody's guess on the 757/767's but they do tend to fill good gaps for larger loads.
They have option slots on 777's from 2010 , but no variant is stated.
I would guess more 777's (maybe some -300's) and possibly 747-800
I think A380 is out of the question, and the still developmental 787 / A350 perhaps a long shot - - BA certainly learn't some lessons with the teething probs of the 777 GE90's and the 767 engine pylons.............