The current product cycle does not permit any revolutionary change for foreseeable future:
1, B777-200ER to B747: will not see any changes at all until their end of life cycle. That means the current CW will last until 2020 and beyond
2, A380 and B787: Minor changes may occur but that would be the same seats for A350. Thus it is safe to say that current CW seats on B787 will last until 2023-2025; Unsure about A380 though, they might get the A350 CW seats some time around 2019-2022.
3, Coming A350: Seats already finalised and I do not think BA would invest that heavily to abandon the already new-ish seats. So the A350 CW seats cycle will last until 2025 and beyond.

If you like seats on AA, CX or even DL and AF. Fly with them. Unless BA's market position is seriously threatened, I do not see BA make big changes ahead following its lifecycle of the current and new coming CW seats.

Any way BA's new motto of cost cutting means no capital investment that would impact on cost cutting. A better CW product beyond the current and force coming Mark III is a waste of money under this motto.