+1. For the Flyertalk crowd (and honestly, consumers in general), the best outcome of this is for AA to emerge from bankruptcy on its own.
A takeover by DL is never going to happen with the current DoJ.
A TPG takeover would very likely devalue AAdvantage significantly. I've seen it wrt HHonors and Blackstone, to the point where I'm currently wondering why I even bother booking personal stays with them instead of Priceline. I seem to get similar treatment as a Gold with Hilton that I do as a PCLN customer at a random hotel, and I'm paying a whole lot less with Priceline. Casual customers would feel it in increased fees, decreased frequencies, and other penny-pinching moves.
US is an interesting possibility. The route networks compliment each other quite well, even if there is some slight overlap in the northeast, and PHX has enough slots controlled by US that would allow a combined AA/US to use it as a base for flights to Asia from the western US. I don't fly US nearly enough though to be able to judge how their penny-pinching might affect AA's F/J/Y products.