Magic's recurring villains, for whatever reason, tend to be divisive when they appear in card form. More controversial even than Bolas and the Phyrexians are the Eldrazi - the non-Euclidian monsters that descended upon Zendikar in Rise of the Eldrazi, the first set since the ordinary block structure was set down to break the convention of a large-small-small block. The true - non-Drone, non-Spawn - Eldrazi were unique in many ways - for being colorless nonartifact creatures, for the annihilator keyword, and for their sheer size, being among the most expensive and biggest creatures in the game.
And, according to Mark Rosewater on his Tumblr blog, they'll menace us again. When Tumblr user brownphish asked him, "I recently joined magic and I missed the Rise of the Eldrazi set. I'm really interested in them and was wondering, Is there any chance that the Eldrazi will return in a near future set?" Rosewater answered:
I doubt we’ve seen the last of the Eldrazi.
Rosewater has said similar before, but the latest information, as the design stages of upcoming sets roll on, is always the best. Naturally, the return of the Eldrazi doesn't necessarily mean the return of annihilator nor of colorless Eldrazi, given the nature of why the beings actually became that way on Zendikar (in brief, they were sealed into the hedrons by the colorless fire of Ugin, the permanent-breaking powers of the Lithomancer, and Sorin's undeath). The Eldrazi can appear in any form physically, being creatures purely of the Blind Eternities, as long as it's alien. Who knows - someday we may have four-color Eldrazi to contend with!