I suppose at present, it's tough for a manufacturer to introduce, say, a new film SLR, when there are such good ones available used for pennies. There are a few makers out there of course, like Cosina, Phenix etc. I think the reason Cosina can make a go of range finders is that even the ancient, battered old Leicas are still expensive. SLRs are different as you can get a practically new Nikon FM3a for not that much. Large format is still well catered for though with new cameras, and medium format is fairly well handled too.
I think if Cosina can work out a way to sell an SLR against practically free used ones, then I think they may try again.