Well sort of. Back then it was being called “Mozilla Developers Preview (1.9.3 alpha)”. The odd naming was due to this being a preview of the new Gecko 1.9.3 rendering engine and what likely would have become Firefox 3.7 (Firefox 3.6 runs on Gecko 1.9.2.x) . There were a total of five Alpha releases between February and June 2010. Then it was decided to scrap Firefox 3.7 as well as Gecko 1.9.3 and move everything on to Gecko 2.0 and then also start labeling the releases as Firefox 4 Beta in July 2010.
So, here we are 1-year later and we are still waiting on Firefox 4. Beta 11 just shipped earlier this week and Beta 12 is still in the works. If Firefox 4 ever gets out of the Betas then it will be the release candidate builds before the final release. Mozilla keeps saying they want to get Firefox 4 out on the market before Microsoft does with IE9. While there is not an official release date (later this year) yet for IE9, Microsoft did launch IE9 Release Candidate today. This means Mozilla is now behind in this browser release war.