First, I have no knowledge of what changes might result from post-ATI "alignment" of the BA/IB/AA FF programs. They might be major, or they might be trivial, or they might not happen at all. However, my personal view is that given AA's more liberal earn/burn profile (with exceptions) it seems to me that BA will have to move more toward AA's system rather than AA moving closer to BA's, given the relative size of the programs. Thus if I were starting now I'd want to use any mileage-earning opportunities to pad my AA account (since they're more plentiful) so that the miles would be more "useful" down the road, presuming that one's mileage balances and (relevant to AA) lifetime status are "grandfathered" forward into whatever new system emerges. But that's just me speaking from the context of my own travel patterns.