Pretty much - most corporations have just barely (as in 2-3 years ago at most) updated from XP to Windows 7.
Good luck with pushing 8 to the corporate world... it's about as adoptable as an angry badger with syphilis.
More and more, I'm finding myself working at places where I really don't have to use a Windows UI if I don't want to. Right now I'm typing this on my corporate-issued MacBook Pro, and only rarely do I bother logging onto a Windows server (vSphere client, and even then only out of habit since the web-client works pretty much as well).
Don't get me wrong - Microsoft will still be in the business world for a goodly long time - we still use Outlook/Exchange, Active Directory, and even Sharepoint (for HR/Corp crap - all the important stuff is on Confluence.) Thing is though, Microsoft's hold in business is beginning to show cracks, and I suspect in about 5 years, there will be a bit of a crisis in Redmond...
Don't be so melodramatic. I think you don't understand large corporations. I work for a fortune 20 company and at the office Win8 has been the standard for well over a year. It requires freeware start menu programs for sure but otherwise it's no less usable than 7 or xp. Of course, "mainstream support" is probably also irrelevant for any corporation since they will have their own support contracts with vendors such as Microsoft. I'm sure lots of small businesses are an exception to this. For them, the win95 (or whatever os it came with) pc that is still running may be just fine.