With the anticipated release for the next ablum, with two backstories on what happened after Plastic Beach, Gorillaz drummer Russel has this to say about the next album at Puss Puss Magazine. As seenhere

"You can expect whatever you like. What is coming will come, wheter you expect or not."

"What's important isn't what happening next, but what's happening right now. That's all you control. And, listen, me and Gorillaz - that's two separate things. Our paths entwine, the seperate - like a messed up pretzel." 

Meanwhile, he was asked about his favorite rappers and he had this to say. 

"Thats like trying to pick my top three favorite cat videos. Just not possible. Let's lose the hierarchy, there's enough of it out there already. But I'll give you three, in no order.. If we're talking BK, I've got to say Biggie. Who else? Then I'd pick MF Doom. Underground legend. Born over there but spent most of his life stateside, the opposite of my deal. And for someone new, check out that kid Earl Sweatshirt. Great name, fresh sound."

Implying, that these new rappers might come in the album. Me and RadicalEdward will keep you posted on more news about the album. 

The full intreview is right here, on this wiki.