Anything new will have to come along with the type of revolution that came along with Unix. Nothing was going to topple IBM until something came along that made them irrelevant. I'm sure they have the mainframe market locked up, but that's just irrelevant. And the same thing with Microsoft: until something comes along that makes them irrelevant, the entry fee is too difficult and they won't be displaced.
"Unix and Beyond: An Interview with Ken Thompson," 1999