LLVM 3.8 release manager Hans Wennborg sent out a release status update to say that the release hasn't been tagged but they're running slightly behind schedule. However, he remains optimistic that they will be able to get the 3.8 release done soon.
Among the blockers are some crashes, issues with loop vectorization, an AA performance regression, and other issues. Those interested in finding out more about these last-minute LLVM 3.8 blockers can read this mailing list post. If you want to find out more about the new LLVM 3.8 features, see this feature overview I had written earlier in the day.