False premise
You posit, "what if MS were to suddenly, out of nowhere, disappear?" ... yes, that would leave a vacuum. But the more reality-based, appropriate question is, what if IT and computing evolved away from MS because other products offered a better business value? If MS were to fail because of that evolution, would it be a bad thing? Of course not, no more than it's a bad thing that Japanese car companies out-innovated and out-"qualitied" American ones.
MS absolutely does produce business value, but too much of their dominant position is based on negatives - "have to use them because of critical software that's Windows-only", consultants and integrators that don't mind the overly complex administration and debugging of problems, because of the job security it provides, the resellers in the same boat, etc. Isn't there a classic business evolution cycle where "people use the product because they have to" is toward the end of the cycle?
