The download page for the new RRC Beta warns that you should not try to integrate the Beta version with a Jazz 2.0 product. My understanding is that Jazz 3 will be backward compatible with 2.0 product.

Our firm plans to remaining on RTC 2.0 for a while, but is interested in exploring RRC 3 in a sandbox environment for planning purposes.

Is the warning message above just a temporary situation?

If you install RRC V3 in a separate environment with its own Jazz Server, separate from the RTC environment you should be able to configure the jazz server to recognise each other as "friend"'s and allow cross linking of work items to requirements, using OSLC V1 specifications (V3 products are using V2 specification).

This said, as RRC V3 is a beta environment I caution creating too many links between RTC work items and RRC requirements - as beta code usually does not provide migration utilities between versions - and any links created might need to be manually deleted in RTC. Best create a sandbox project in RTC that can be easily deleted.