I'd say the last two gens were pretty balanced. Especially last gen. GTA may have been the highest seller but I wouldn't say it's genre dominated. It just meant that GTA dominated. And sandbox games definitely weren't releasing like crazy like FPS's are this year. 5th gen, everything was pretty balanced as well.
With that said, I'd say FPS will still be pretty dominent but console hardware will finally allow some decent MMO's which could be big. I remember SONY pushing for them this gen but hardware restraints likely got in the way. There was also a push for MMO's on 360 but by the devs of MMO's. Sadly, MS's restrictions on XBL didn't work well with what devs want. Online is huge now so I wouldn't be surprised if all 3 publishers pushed to make online games of all kinds generally more easier to get out there on consoles.
4 ≈ One
