We had already told you that Mozilla will launch Firefox 4.0, 5.0, 6.0, and 7.0 this year.
Firefox 4.0 is already launched and Beta version of Firefox 5.0 is out for testing.
Mozilla has put the release date of Mozilla Firefox 5 on their wiki and it will be coming on June 21, 2010
Mozilla is also set to release Firefox 5 Mobile, Thunderbird 3.1.11 and SeaMonkey 2.1 on the same day, June 21.