Considering the success of Far Cry 3 (and the Blood Dragon spin-off), it should be no surprise that Far Cry 4 is most definitely in development. According to industry insider Superannuation, Far Cry 4 is set in "the Himalayas or adjacent locale." Oh, and it has "monsters."
Ubisoft has obviously declined to comment, but the apparent leak occurred on Twitter, with Superannuation tweeting two hours later, claiming the original tweet was meant as a direct message.
Far Cry 4 sounds super boring from the rumors. It's the third game more or less transposed to the Himalayas or adjacent locale + monsters(?)— superannuation (@supererogatory) February 5, 2014
Well, I thought I sent that as a DM. Oh well. ¯\_(?)_/¯— superannuation (@supererogatory) February 5, 2014
Considering Ubisoft has already done the jungle, and desert thing, a snowy environment would certainly be a nice change, especially with some sweet weather effects and maleable snow a la Company of Heroes 2. The "monsters" rumor is a little more disturbing though. Excluding Blood Dragon, Ubisoft's Far Cry games have been steeped in at least some sense of realism. The original Far Cry, developed by Crytek, featured "monsters" known as Trigens, and they were arguably the worst part of the game – and by "arguably," I mean, if you don't agree, you obviously didn't play the otherwise exceptional game. That being said, one common "monster" associated with the Himalayas is the yeti, which could actually be kind of cool. Maybe yetis would be super rare and there will be a quest to track and hunt one down? I'd be okay with that.
Nevertheless, these rumors should be treated as such. There is absolutely no proof or confirmation of either of these things, not to mention plans can always change.