Rock used to be much more popular on radio a decade ago, but that's dead at the moment. We have to remember that pop music is a term used for the most popular music on the radio. Chuck Berry was considered "pop" music back in the day, Elvis and the Beatles were pop too.

I think the reigns of female pop has died down a bit and so has dance pop. Right now, singer-songwriters seem to be getting all the buzz, hype and attention. Rap music has seen a resurgence as of late with the likes of Drake and Big Sean gaining huge momentum on the charts, because let's not kid ourselves, rap was a little dead in the early 2010's with the electronic sounds taking over. Now it's back.

I think once everyone is fed up with popstars like Ed Sheeran and Adele, we'll be going more rock. But to answer your question, the music that will continue to be mainstream will be rap and male pop with a few exceptions here and there, of course.