From the 'not far now' files:

As I had predicted when Mozilla Firefox 3 Release Candidate 1 (RC1) came out,  RC2 is now officially in the works. Considering that code quality and stability should always be Job #1 this is the right decision - no need to rush and then upset users with a sub-optimal experience.

In a mailing list posting, Mozilla Developer Mike Beltzner noted that RC2 is not expected to impact a final delivery of Firefox 3 for mid-June. In order to make sure that happens Mozilla is being quite strict with the patches it is accepting into the RC2 stream. Beltzner wrote:

Many of the issues to be fixed in RC2 have already been patched, reviewed, approved and landed, thanks to work done last week to identify and drive the bugs into the product. Several localization  
updates have also been accepted. Please note that just because we've decided to produce another release candidate does *not* mean that we are accepting new patches - only those which fix issues that have been identified as required fixes for RC2 will be accepted, and even then your patch must come with a risk assessment and tests.

Sounds kinda tough to me - but it's a good kind of tough. Without some kind of strict control over patch inputs the release process could easily spiral out of control.

Officially the code freeze for Firefox 3 RC 2 is Noon PT today with final QA by Thursday June 5th.