During Tokyo Game Show 2016, Ryozo Tsujimoto, the producer of Monster Hunter Stories, announced that Capcom is working with a major Hollywood studio to make a movie based on the Monster Hunter series.
At the time of writing Tsujimoto is unable to provide further details and didn't mention which studio was involved in the project. He also hasn't even specified whether it will be CGI or a live-action movie, nor did he hint at a possible release date in the cinemas.
Basically we don't know anything more than that it's happening, thus we'll just have to wait for more details, hopefully in the near future.