those sound like good ideas, but you have to remember the problem: whoever does it will be spending time and money on what will be, in the end, a labor of love. there are qicker and easier ways to make money than making and then marketing an os for a defunct sampler/sequencer, regardless of the size of the potential user base.
the way to do it would be for a large group of mpc users to band together and hire someone: like say 4000 people give ten bucks a piece: im sure someone would do it for forty grand
but the next problem will be: what should the upgrade be like? 4000 people may have 4000 different ideas of how the new os should be...
and how do you show those 4000 people that you are not just running a scam?