Mozilla has taken the new roadmap that plans for more releases seriously. The effect of that is that today Firefox 5.0 was released. It should be faster, easier to use and more secure. On the first glance I haven’t found any striking differences compared to Firefox 4.0.1, so the changes are mainly under the hood.
Firefox 5 is already available in all the featured languages and for all supported operating systems.
Mozilla will continue with frequent releases and will release two more major versions (6.0 and 7.0) by the end of 2011. We can expect to see Firefox 6.0 in beta channel on July 5th, but you can already test pre-alpha releases of Firefox 7.0a1 in the nightly Aurora channel.