User blog comment:Kogath/Monster Hunter: World Discussion/@comment-6050823-20171107103543

On that stream for the Rotten Vale, Capcom said that they revealed about half of the monsters in MHW so far. The other half that hasn't been announced yet.

Source: https://youtu.be/vQp6cBHPNKo?t=622 (It is a bit after the timestamp).