Amateurs? I know some people who code for Linux/Open Source. They are neither amateurs nor partime programmers, quite the opposite in fact.
So be carfull with your labels. The truth will surprise you.
As for budgets, even the largest corps are concerned with the bottom line. If they can get the same bang for the buck or less, you know they'll consider it closely. In fact many large corporations have outsourced their IT due to budgets and the fact that they're locked into M$ and their ever increasing pricing structures doesn't help.
So again, looking for alternatives to lessen those expenditures will *always* be an option.
Conjecture as to what will happen is entertaining, but most people live in the here & now.
So sorry about that but for the desktop, right now there is Windows...then there is whatever else is out there which is only about 5% of market share.