Milwaukee has already lost an MLB team once and they almost lost the Brewers in the 90s. It could easily happen again.
Vegas is still not inevitable. If public officials balk at giving tax dollars to a new stadium, I guarantee you'll see some of those other options come up.
MLB expansion talks will get serious the second the A's and Rays stadium deals are inked. The loss of RSN revenue is going to be the catalyst to bring in some new cash from expansion fees. Everyone seems to know this and various groups of investors have been getting their ducks in a row...Portland, SLC, Nashville, and Raleigh. Right now I would predict that 31 and 32 will be Nashville and Raleigh unless one of the groups out west mounts a more serious campaign. When they go to 33/34 I suspect they will more seriously consider international expansion, with Monterrey MX being the most likely target.