If you are happy with your screen surface, then there will be no problem using it with a 4K projector. The light path will still be the same and you should be happy.

That said, at 100", if you can't go larger, there are certainly some 85" TVs on the market which will look very good and may be a better option.

Be aware, that IMO, many professionals install screens which are far too small for typical viewing. You should have at least 10" to 12" of diagonal for each FOOT of viewing distance, or you will be giving up resolution. So, at 12' viewing, you should be at a 120" diagonal to 144" diagonal, and I might settle between at a 133" or so diagonal image.

But, even entry level white screens, in a good room, look really good. The better the ROOM is, the better the image will look. Grey screens, are a band-aid, not a way to actually improve image quality. So, a dark room, with dark ceilings, and dark floors, will make any projector look as good as it possibly can. Throw a good projector in and you will be blown away.

But, not at 100" when TVs are starting to approach that size in stores for a few thousand dollars.