It is an assumption, since no one actually knows if he’s going to make an appearance in the ride or not, as Disney has given us crumbs regarding what the experience will be like, the plot, new characters and songs, etc. People are taking said crumbs and trying to build a whole gingerbread house with them.
This ride is not based on the movie, so I’m perplexed as to how you and others find it odd that there’s a possibility that Facilier won’t be in the ride. They’ve said, multiple times now, that the ride takes place AFTER the movie. This is not going to be a ride-thru of PatF.