Mozilla has announced that it will release the first update for Firefox 4 on April 26, about a month after the original release, back in March 22.
New with this release is that Mozilla will start using code names (somehow related to the main branch codename, in this case Tumucumaque) for udpates as well, as a way to help developers that follow Firefox development closely, more clearly understand what is coming when.
As explained in the Mozilla Wiki, it is not unusual that in the middle of an update development (say Firefox 3.6.20), a critical security or stability bug is discovered that forces Mozilla to put thing on hold and rush a quick update, which would then become 3.6.20. All previous bug fixes are then released with Firefox 3.6.21, causing some serious headaches to developers when trying to spot bugs targeted for the next release.
With code names, Firefox 4.0.1 is Macaw, no matter what happens between now and April 26. If, say, a zero-day vulnerability is discovered, the emergency update will get a new codename (Anteater, actually), making it perfectly clear what each one is about.
In related news, Aurora, the new development branch that will enable Mozilla’s new faster development cycles, will be created tomorrow.