Well, put it this way... the Montreal stadium going up is easily expandable to MLS suggested minimums, the Vancouver stadium proposal is impressive to say the least (and complete privately funded, yet the city may actually be trying to stall it out !?!?!?!?), and Merritt Paulson knows that Seattle going and Vancouver wanting to go means Portland either better move or die... and Portland has the best fan base of the Northwestern trio in more ways than one. The timetable is suspect, but I tend to think ALL Cascadia's teams will eventually make the move.
Rochester is going NOWHERE. The fan base has dwindled, and the current issues with one of the owners isn't helping. If anything they and most of USL1 (save the supposed prospective California teams) would benefit from the Northwest teams getting out due to better geography. I don't know what Frank DuRoss (not the owner in trouble, BTW) has done to lose the fan base other than not win the league every year. I do know he pulled a trick involving Pae Tec Park financing that probably sent signals high up that he's playing fast and loose with someone's money (public funds being potentially someone).
MLS does have enough suitors in non-USL1 markets (St. Louis is all but in, Philadelphia is getting groundwork done) that USL1 need not completely be raided. Without a western presence, it'll probably thrive a little better.