RPM 5.0b4 was released today.
Find it under: http://rpm5.org/files/rpm/rpm-5.0/

This release is the LAST BETA VERSION in the soon finished RPM 5 release
engineering BETA phase and is fully stable and hence can be test-driven
by you in real packaging environments. Please give it a try on as much
different platforms and send the RPM 5 developers your feedback under
rpm-devel@rpm5.org. If no more major bugs are found, we'll release RPM
5.0.0 within the next week.

                                       Ralf S. Engelschall
                                       rse@engelschall.com
                                       www.engelschall.com

PS: Please notice that RPM 5 it is *NOT* a 100% compatible drop-in
    replacement for RPM 4, so if you want to test-drive it you might
    have to at least slightly adjust your packaging environment first.