I wouldn't plan anything around a rumored ATL base. NOTHING has been announced for any new bases. If you plan on MSP, DTW and MEM you'll be fine. Will an ATL base open in the future? Anything is possible.

Upgrade mins are something like 1,000 flight hours at XJ and a bunch of other things... all can be reduced to ATP mins so that it prevents the hiring of street captains. Of course, you need the seniority as well.