My guess is that it'll be like UA and CO before the merger completed. Chase ran both their card programs and Citi runs them for both AA and US, and post merger you will have one combined acct with mileage from both accts integrated into a "new" AA FF acct (not a new acct being generated but new in that it is an integrated of both pre-merger accts). I say go for broke and churn both the World Elite MC for US Air and maybe the Top Tier card for AA for the miles and bank them.