I haven't seen anything related to Request Tracker v.4 on Fedora sites. bestpractical.com claims it's a major update with lots of bug fixes and improvements:
http://www.bestpractical.com/rt/whats-new/

What is the status---is anyone working on / planning to package v.4? I suppose it won't be a simple package upgrade given that the current package is called rt3 :)