I've read articles that explain how to enable Visual Studio 2010 managed extensions to get them working with Microsoft Visual Studio 11 Developer Preview
Running VS2010 Gallery Extensions In VS11, Meet Git Source Control Provider
However I haven't been able to apply the same logic to Resharper. Although it's a managed extension now, it doesn't appear to be packaged in a VSIX file, so I can't follow all the steps in the above mentioned article.
Whilst I can't find an official looking page on JetBrain's resharper web site, I did find a reply from a JetBrain's engineer
The upcoming ReSharper 6.1 will have initial experimental support for Visual Studio vNext.
http://devnet.jetbrains.net/message/5320971#5320971
Resharper 6.1 has now got experimental support for Visual Studio 11, albeit via a separate download to the normal 6.1 installer: http://www.jetbrains.com/resharper/download/index.html#related
Blog post explaining the current level of support in VS11: http://blogs.jetbrains.com/dotnet/2011/12/christmas-is-here-resharper-61-dotcover-12-and-dottrace-452-released/