I haven't looked into AA lounges but with the exception of my home airport in PHX and during some international trips in PHL I haven't used a club that wasn't UA. It just seems like there are more UA clubs where I fly a lot (DEN, ORD, DFW).
This was actually one of the things I was most dissapointed in losing with the merger. And at this point it is one of the only things I know I'll be losign for sure (and UA code shares).
I don't know if I have any real advice for you at this point besides wait and see. If it were me, the only way I would renew at this point not knowing the future is to get the 5K PQMs (which is the only reason I signed up in the first place).
You could check ebay for some United passes if you know you will really want to use the club in the meantime.