My post, as you probably know, is based on reports about cities that seem to be under consideration as we type. That tells me they have the resources/plan to get going sooner, rather than later, and the commissioner really wants to get that 16th team.
As for my own preferences, the Columbus, Ohio, idea is interesting: expanding regional area that has supported hockey and soccer teams. Along the same lines, what about a Kansas City?
Your reminders about the southern teams ring true and I'd think the W wants to make sure this works. If any southern city is chosen, I'd think Nashville might be chosen (and I'm not even sure about that.)
My gut (as of now): Denver or Philly.