I feel like all of these are going to be a squash match for the bigger guy.
In the history of MMA, to date, the only guy in my opinion who went up a weight class and beat the legitimate number 1 guy in a weight class above, so far is BJ Penn.
BJ in his prime was a special, special fighter. There's a reason why it hasn't been done again in 20 plus years, and looking at the guys potentially going up a weight class, as good as they may be, I don't think they will pull it off.
The only potential match up would be Islam moving up a weight class to fight Belal or Shavkat. But if Belal wins, it won't happen, and if Shavkat wins, I think Shavkat will run him over. If he struggled against Poirier, imagine against Shavkat? I can see him beating Belal but he won't fight the guy.