A basic installation of TFS 11 Beta will install SQL Server 2012 RC0 Express Edition and includes a license for SQL Server RC0 Standard Edition. TFS 11 requires SQL Server 2008 R2 or SQL Server 2012 (SQL Server 2008 is no longer supported). I received word from Microsoft today that TFS 11 will include a license of SQL Server 2012 Standard Edition (only for use with TFS 11), so what does this mean for you? It means that you can safely choose the option to install SQL Server 2012 RC0 that is supported with the TFS 11 Beta; No worries about having to move back to SQL Server 2008 R2 because of licensing.
SQL Server 2012 is now officially released, but don't jump the gun; install SQL Server 2012 RC0 with your TFS 11 Beta and upgrade to SQL Server 2012 RTM When TFS 11 releases.
Read more about upgrading to SQL Server 2010: http://technet.microsoft.com/en-us/library/bb677622(v=sql.110).aspx
Did you know that you can upgrade to TFS 11 Beta now and it will be supported for production use? Read about the Go Live license for Visual Studio and Team Foundation Server 11: http://www.microsoft.com/visualstudio/11/en-us/downloads/go-live