According to a Eurobricks user, these are the names of the 5 rumored sets that will be coming out in the summer of 2015. Do these seem real to you?
70791 Skull Warrior
70792 Skull Slicer
70793 Skull Basher
70794 Skull Scorpio
70795 Mask Maker vs. Skull Grinder
AND there will also be a Bionicle polybag released this spring, but its contents are currently unknown.
And finally, the winter wave of Bionicle sets are starting to pop up before the "street date" of January 1st. I will probably go hunting for some sets at some point in the future, and if I find 'em, I'll review 'em! I've promised it before and never committed, so I think I'll actually try out reviewing!