They wouldn't switch because of the tremendous cost involved. You have to replace a bunch of already functioning boxes, and for what?
You'd have to expect a pretty large decrease in IT support staff to recoup that cost. For businesses, it's all about the bottom line on the spreadsheet, and the cost of switching from any one OS to another is rarely going to be justified.
Much more likely is a company supporting both for a time, and switching over to the new OS on all new purchases, or allowing employees to choose.
But most companies (in my experience, before some little punk says "but where's your data") tend to replace all their kit every 3-5 years anyway. Those "old" computers didn't suddenly get slower. Unless you're in a business where raw CPU grunt matters, there's no real reason, but they do it anyway.
It's funny, loads of companies in the late 90s ripped out their Unix CAD workstations and replaced them with high-end PCs running NT . No-one batted an eyelid at that. Now we're talking about replacing average PCs with Unix workstations and everyone's like shyeah right.
I think that cycle is a lot longer than 3-5 years now, especially with the economy the way it is. It probably was that way for a while (and was probably even shorter before that) but there seems to be little justification for it anymore. We're finally at a point where a computer from 3 years ago can do everything we need it to do today, and not too slowly either. That's a relatively new development.
You'd have to expect a pretty large decrease in IT support staff to recoup that cost. For businesses, it's all about the bottom line on the spreadsheet, and the cost of switching from any one OS to another is rarely going to be justified.
Much more likely is a company supporting both for a time, and switching over to the new OS on all new purchases, or allowing employees to choose.