Following a set of leaks that outed the game, Square Enix has confirmed that "Nosgoth" (aka "War for Nosgoth") is in active development and set in the Legacy of Kain universe. It won't be announced at E3, but the company has explained a little about the title regardless.
In a statement to VG247, Square Enix community manager George Kelion clarified that Nosgoth "is not a traditional Legacy of Kain action-adventure game." He said, "Nosgoth is set in the same universe as previous LoK games, but on a different branch to the Blood Omen and Soul Reaver series. The community should not be thinking of Nosgoth in terms of a single-player experience."
He confirmed that Crystal Dynamics is not working on the game, or any Legacy of Kain game for that matter. He also noted that Square Enix usually wouldn't respond to rumors, but given the leaks it "wanted to just give folks a bit more context for the direction, rather than just batten down the hatches."