I feel Khabib is the next big star, whilst he is already a star in Russia he still hasn't broken through the Western mainstream audience yet. If he manages to beat both Tony and Conor then he will be the next star for sure.
Darren Till and Mike Perry have the potential to be WW stars. I see both of them as future champions. Mike is truly the whole package and just needs to penetrate the Top 10. Darren is the same, the beautiful thing is that both of these guys are young.
Israel Adesanya is obviously the whole package and is the most likely MW to reach star status.
As for the lighter weight classes the only person who I see becoming huge is Cody.