Reheat,
The peak birth rate during the post WWII baby boom was 1960. Fast forward that lot to age 60 and the year will be 2020, so on the surface, I am not convinced they've all retired just yet. I'm not saying you are wrong, as I don't claim to be particularly well informed on BAs retirement issues. Have they released any studies on the matter?
Smell the coffee,
300 new pilots over two years is a tiny number for BA. When you consider that probably half or more would be DEPs, that leaves no more than 75 per year for SSPs from Cabair, FTE and OAA. These sort of numbers don't seem like they would create much pressure for a cadet programme unless BA really do fear they won't find the quality they want because of the other airlines with cadet schemes taking them first.