Mozilla release Firefox 5 a couple of days ago. This comes just barely 85 days since the release of Firefox 4. They only put out 2 whole versions, 4.0.0 and an update 4.0.1 before releasing version 5.
Why so quick? The official word from Mozilla: We are moving Firefox to a rapid release schedule.
Some have speculated that there could be security issues with version 4 that this new release addresses. I can’t verify that statement. It is just what I have read in a few other threads and postings.
If they keep this new rapid release schedule at or around 85 days in between it won’t take long to see a Firefox version 10.