the only person worth listening to so far on this thread (as so often happens) is jdiver.
no major airline would dare piss off their most frequent flyers.
and if they ever did competitors would likely make some pretty huge match offers to move the core business over!
i have miles in both aa (1 million+) and usair (90k+) and i'm 100% confident they'll be consolidated.
tho i'm still to this very day 100% pissed with what aa did to my twa lifetime ambassador club membership.
that said, however i have more than received the value back (often with the help of flyertalk) from an aa program that is very generous to its exp's...