Firefox is moving to Chrome’s development model of rolling releases, getting away from the large, cumbersome release schedules that have been the norm for the project for a very long time.
Of course, the first thing they need to do is release Firefox 4, finally, and then ramp up the new production model to try and release new features as they are ready instead of setting milestones and rolling them into large releases.
I welcome the change and hope it will push Firefox ahead as fast as Chrome has been moving.