For everyone who want to move to Visual Studio 2010 RTM and expect to be able to work with the current release of WPDT CTP, sorry let you that the current version of the WPDT is not compatible with VS 2010 RTM.
For more information please read the post of Tim Heuer on the Silverlight Forum: http://forums.silverlight.net/forums/t/175181.aspx
So for now we have to be patient until they release an updated version of the WPDT.
If you want to get notified when they release the updated version go to the following link: http://www.microsoft.com/windowsmobile/en-us/cmpn/vslaunch/default.mspx
Regards,
LP