With 6 more 77W, BR will have 28x of the type by 2017. That's a pretty good size fleet.
777NG orders will be a ways down the road obviously but BR is doing Boeing a real solid favor by taking more 77W and 77F in the last 2 years of production so that favor will be repaid on good delivery position and/or pricing on the 787-10 and 777NG.
BR will need 14x 787-10 to replace A330s (currently 11x A332 + 3x A333) frame for frame. It is interesting to note that GECAS (BR's main leasing partner) has 10x 787-10 on order.