After Windows 8? Linux!
Windows 8.1 will have a semi-return of the Start menu, but most importantly will allow the option to boot directly to the desktop instead of having to put up with the uber-bullshit “tile” interface that they thought was a good idea. Microsoft’s inability to recognize the different needs between tablets (which they have little market penetration with) and desktop PCs will/has lead to people staying/returning to Win7, or jumping ship to Linux.
What would I like changed? Better security, more stability, better compatibility with non-Windows stuff (OS X and Linux are both Unix-oid operating systems; Windows is the odd one out), better backwards compatibility with previous versions of Windows, and to remove that tile interface and shove it so far up their ass that it tickles their brain. I’m not normally that crude, but I _really_hate that UI!