Jeff just announced on his blog that Team foundation server Release candidate is coming really soon now.(Very early February if all goes well)
There will be upgrade support as well for your current running Beta 3 refresh servers running. So make sure you are upgraded to Beta 3 refresh and then you will be OK. The amount of effort it will take to upgrade is not known by me yet, but I hope it’s less work as the previous upgrade from Beta 3 to Beta 3 refresh. I did find this post on the Team Foundation blog that describes the upgrade scenario, now hope that the scenario’s will be met so it will be a smooth ride.