The RDL files are the base of the reports being deployed. The format for these don't change unless you upgrade the SQL Server.
Seems like you should be able to create a new reporting project in VS2010 and import the report RDL files into that. I have not tried sharing files between different versions of VS so you may end up with difficulties on the VS specific option files and such for the deployment. So you may want to store the RDL files in a different folder than the VS specific project files and see if that helps.