UPDATE (5/10/2012) This has been solved! (Albeit two years later) Go download SQL Server 2012 Data Tools!
So, you’re migrating to Visual Studio 2010 and you want to open your reporting services projects… Not going to happen!! According to the SQL Server development team, they have heard the suggestion and resolved not to add that feature. So, if heaven forbid, you have a solution that has a reporting services project in it and another type; you will be switching between VS 2008 and VS 2010. The problem stems from the fact that Business Intelligence Development Studio (BIDS) is implemented by the SQL Server team and Visual Studio is in the Developer Tools department. Apparently they don’t talk and the SQL Server team releases BIDS when they feel like and on the version of Visual Studio they feel like.
Maybe they need to change the system?
Woody Press 
Glad I didn’t get too far along with seeing how VS2010 and RS might work together. I’ve seen this reported back in March but was hoping by now it had been resolved. Seems odd but RS has a number of integration hooks into VS and if its not adding any new features there isn’t that much incentive for them to migrate to VS2010…. After the install is finished for VS2010, my development server now will have VS2005/2008/2010 all installed – atleast (I assume for 2010) that these all run side-by-side..
Thanks alot – your answer solved all my problems after several days srtuglging