Yesterday we released the final release candidate for Update 4 for VS 2012 and TFS 2012.
We’re on track to release the final versions in a month or so. I encourage you to try them out and let us know if there are any last minute issues we need to fix. One thing to keep in mind – If you install TFS 2012.4 RC4, you will have to upgrade to the final TFS 2012.4 release before upgrading to TFS 2013. There is no upgrade path from the Update 4 RC –> 2013 RTM (other than by installing Update 4 RTM first).
You can find the full list of fixes in Update 4 in the KB article referenced above (I count about 68 bug fixes in all).