I would guess that at least for large format cameras, the same people who are building them now. Maybe not the exact same people, but people who enjoy using the format. Large format hasn't been cutting edge for what, about 100 years now, and people are still using them and building new ones.

By the way, I got my first 8mm cine camera earlier this year after seeing the quality of some movies that my Grandfather took in the 1930's and 40's, it is a blast to use. It sure beats the heck out of that video camera that I used to use.