As per the information by microsoft partners Program site, Microsoft next generation Windows 7 Release Candidate is available to Technet and MSDN Subscribers now. It will be available to public on may 5, 2009. But accroding to arstechnica, The build is not yet available to Technet and MSDN subscribers.
From a reader chat with Microsoft Online Concierge “Currently the Windows 7 RC has not been available through the TechNet subscription yet, only the Microsoft OEM partners such as Dell, Siemens are taking part in the RC’s this period of test.”