On its mailing list, Mozilla has revealed it has around 160 hard blockers to fix, before proceeding to Release Candidate stage.
Both the RC and the final version would arrive in February, according to Sicore. Mozilla was originally planning on having Firefox 4 out by the end of last year, but it had to delay the release till 2011. Last month, Firefox 4 Beta 8 was released for Windows, Mac OS X, and Linux 32-bit/64-bit, with support for 57 languages.
Mozilla's roadmap says it still wants to release a Beta 9, a Beta 10, and at least one Release Candidate build before the final version."