The biggest problem when upgrading someone to another operating system is keeping all of their files and settings. The next issue is software (sometimes these can be reversed). With linux, both of these are fairly simple unless you are transitioning from gnome, to kde, to xfce, unity, etc. with a migration. Staying with the same desktop saves hassle, the files will be easy but settings not if you change. Software installation should be the easiest inside linux if you use repositories to install software, or don't have to compile from source for them. Even if you do, it should be one off applications and that happens with windows anyway (try finding the installation file for something that is outdated, unsupported and they downloaded from a website that is belly up).
The biggest issue for linux is almost all of the software created for businesses is windows based. All the tools people use to support them are windows based, and domains are all windows based in most companies. Even games that are created now come out for windows but don't come out for linux. This is slowly starting to change.
Windows 7 was a big change, but not big enough to warrant a complete re-write for software. Some of it had to be tweaked, some of it worked just fine without any modifications. If software works with windows 8, we will see the same thing, maybe a little less compatibility but it works so nobody wants to do the work to convert it properly, they will live with it in the state it is in. The programs that need to be changed, the program is already written for mostly windows so if they can change a few lines of code, or even a whole file it is better than rewriting the whole thing.
It would be nice if everybody wrote software that was os independent and could run on multiple platforms with very little effort, but I do not see that happening. There are a lot of tools that people use that aren't needed in linux, but people grow attached to and know how to use.
I don't think RDP is a good suggestion for legacy applications because the new windows OS is still needed. If you are going that direction and need RDP for it, you can either use the new OS natively or you will have to use RDP from windows to a legacy box anyway.
I like linux, its easy to use, runs well, and I have to fix it less than windows. I don't think we will get rid of windows. It keeps to many people working when you have problems and updates.
P.S. Your comment about Windows having 11 years between roll out... Most computers didn't last 11 years, we recycle ours every 3 years, and Microsoft is trying to get a new operating system released every 2-3 years now.
Grabbing my coat, heard another windows box is having issues.