AA already has a hotel booking portal, operated by the same agency at Citi's portal. Likewise, AA already has a Dining program. Those programs also award Loyalty Points. Spend through Citi's portals to earn ThankYou points will, to some extent, simply replace spending through AA's own portals, and TYP to AA transfers are unlikely to earn Loyalty Points. I don't see anything here that would make AA apprehensive about a "flood" of transfers.
i dont think aa is apprehensive about a "flood" of transfer since they will look at dl and ua and feel that they can devalue and still remain ahead
i disagree that strata elite and premier spend through citi travel portal canabalizes aa's own portal. the cards target 2 different demographics - aa co-branded cards are meant more for people who fly with aa with some frequency, and/or people who are chasing after aa elite status, while strata elite and premier are meant for general travel and people who have no loyalty to any ffp. there will be some overlap, but it is mean to cover a wider market, just like UA and chase, and DL and amex
the potential influx of aa miles will come from existing pool of typ accumulated with citi prestige and citi premier cards if allowed, and simply that more people than before are able to transfer points to aa, especially since the multipliers are higher than co-branded cards, so they earn faster