The Team Foundation Server 2010 Beta2 and RC releases have an expiration date of June 30, 2010.  You will want to upgrade to the TFS 2010 RTM release prior to this date so that you can continue running TFS.  Both Beta2 and RC can be directly upgraded to RTM.  Please read my blog post here on upgrading from Beta2 or RC to RTM.  In summary the process is straight forward:

1. Uninstall TFS Beta2 or RC

2. Install TFS 2010 RTM release

3. Select the "Upgrade from Previous Version" wizard

(Note: Always be sure to have a good backup copy of your TFS databases and system)

To check on your license type and expire date open the TFS Administration Console on the TFS server and on the right hand side of the first node you will see the license information