I was more excited when I heard B.D. Wong was returning. Nonetheless, a lot of people were endlessly moaning disappointed that Malcolm did not appear in Jurassic World. Therefore, I think it is a good strategic move by the film makers to make Malcolm appear in this film. Maybe this time, the fans will shut the hell up be content about the cast.
Personally, I will probably only enjoy JW2-Malcolm if he stops behaving like a standard action movie hero, and will be a bit more like an actual mathematician as portrayed in the novels.
He only filmed for a week so don't expect him having large screentime but that doesn't mean his role is just a cameo. Expect him having like 3 scenes. One at the beginning, another in the middle, and lastly at the end.
If the ending of the movie was filmed in the UK then Malcolm may have most of his screentime at the end.