Well, I'm hoping MS won't go bust for a while, as I'm trying to get my head around VBA and I don't want my effort wasted.
I forgot about the office environment (pretty big omission). I suppose MS is fine in that environment as they have IT depts. All the same, commercial licences of MS products cost lots more than home licences, which cost lots more than Linux and Open Office. If you were a small company, why pay the extra cost?
I suppose most businesses that need special desktop applications would probably still go for MS, just because they have sort of become the industry standard. My previous company developed applications for storing, retrieving and playing video for the television broadcast industry. This involved interfacing with databases and dedicated boards where timing considerations were critical. It doesn't matter too much which operating system was running on the boards, but it's a complication if the database is running on a different operating system. The majority of coders have experience of working in the MS environment, and the IDEs for developing code on Linux don't appear to be anywhere near as good as for MS.
I remember going to some BCS talk, which said mainframes would make a comeback, partly as a response to save electricity. This would not help MS's cause.