I am hoping JetBrains folks will port their suite of .Net tools to other platforms. Since the core of these tools is already cross platform (JVM-based), it may happen faster than Microsoft does to Visual Studio.
Most of the JetBrains products won't be relevant when Roslyn ships. Visual Studio 2015 already ships with many ReSharper features out of the box, with the ability to add the missing ones being made trivial by the new Roslyn APIs.
I definitely won't be running ReSharper in VS 2015.
Microsoftie here. Pure speculation on my part, but Visual Studio in its full form might be one of the most impressive pieces we have at Microsoft - but definitely one of the most complex. Good intentions aside, bringing VS over to *nix would involve a gigantic amount of (costly) man hours...
That would be nice. Then I can use Atmel Studio on Linux