It's more likely that it would make MonoDevelop more strictly VS compatible. It already opens and saves .sln and .csproj files, but my understanding is that going back and forth between VS and MD can lead to problems.

I'm working on a pretty advanced solution right now (F# + PCLs), everything works both fine both in VS and Mono's xbuild.

VS is built with WPF and making WPF cross platform would be one hell of an effort. It sits on top of too many low level windows apis that it would be a ton of work.