Actually, BEAM can somewhat (and probably should be) considered an OS. It's got most everything you'd need baked in and ready to go...
Right now, I'd say the bigger issue isn't he entire OS taking advantage but the applications running within it... in which case, yes, BEAM would be an amazing paradigm shift! :D
I remember SGI adding code to Linux to to make it work on their NUMA machines with 256 sockets and 2,000-4,000 cores with single system image. They were my favorite but not only one. I'm sure some distro out there can handle 50 by now. :)
I'm honestly not sure. I was under the impression that it was limited... but thinking back perhaps I was thinking of the software that usually doesn't take advantage of multiple processes. Also half joking :D
A research OS with the theme of treating the OS as if it were a distributed system.