St. Paul would need a league to play in.The PCL isn’t as much of a stretch geographically...but, presumably, the PCL isn’t the league looking for a replacement for Rochester.
St. Paul would clearly slot into the current PCL, right along with Des Moines and Omaha.
Rochester isn't going away away as a AAA club, they'll just be getting a different franchise, my guess being the Nationals. In this case, St. Paul would basically be replacing Fresno (Washington's current team) who will be demoted to the California league.
That said, from the sounds of it, AAA's structure is also likely to change, either with 3 leagues (east, west, central) or just making the 2 leagues unbalanced, with all of the eastern PCL teams joining the IL, leaving only actual western teams - say El Paso and west - in the Pacific Coast League.