Under legislation due to take effect next year, BA's flight deck crew retirement age will rise to 60 from next year, and may rise further in the future (Virgin's is already 65 by optional contract extension). This change has been known about for a very long time, and will certainly have influenced BA's current policy of not resurrecting the cadet scheme.
BA are currently not particularly interested in taking ab-initios anyway; the 24 they are taking this year (from a variety of schools) are a very small proportion of their total pilot requirement. As we have pointed out several times before, when you lot are prepared to spend up to £100K on your own training, why should BA (or anyone else) offer to pay it for you?
As for BA's manning requirements for the future, I understand that many of those who can go at 55 will still do so, even though they could stay. BA are not expanding, but the cost-saving measures they have taken over the last 4 years have left them short of pilots. Assuming nothing drastic happens in the market, it seems reasonable to assume that BA will continue recruiting at roughly their current rate for the next few years.
Scroggs