If you want to run TFS 11 (Beta) and SharePoint 2010 on the same server, you now have a minimum requirement of 4 GB on the server. It won’t let you install if you have anything below that and it will warn you with a suggestion that you get 10 GB if you have 4 GB.
Although most production servers would have more than 4 GB in the past, I don’t remember seeing that on TFS 2010, so it’s something to keep in mind if you are planning an in-place upgrade. Of course, this is assuming that this won’t change for RTM.
You can see the System Requirements here: http://msdn.microsoft.com/en-us/library/dd578592(v=vs.110).aspx