14 DAY TRIAL // Mozilla plans to notify Firefox 3.6 users that there's a newer Firefox out there and that they can update if they want to. Mozilla planned to offer this notification for Firefox 7 initially, but postponed the move and will now offer it for Firefox 8, which is coming out in about a week.
On 17 of November, 2011, all Firefox 3.6 users will get an update notification, saying that a new Firefox is out, Firefox 8, and that they can upgrade to it.
It's an optional update, they can decline and continue to use Firefox 3.6 and they'll receive updates until Mozilla decides to end support for it.
Firefox 3.6 users have already received two notifications like this, one when Firefox 4 came out and the second with Firefox 5.
Mozilla has held off on any more notifications since, presumably because they would become annoying if they came in every six weeks, when a new Firefox is made available.
Mozilla wants to make sure that users know this is not end of life for Firefox 3.6, it will continue to be supported with security updates for a while to come now.
Since Firefox 3.6 is the last of the 'traditional' Firefox releases, many people and organizations are depending on it and won't update to the newer versions which come with the rapid release cycle.
So Mozilla is stuck updating it until it has a solution for this users, aka until the extended support release (ESR) Firefox is ready. The initial ESR release was supposed to be either Firefox 8 or Firefox 9, but it looks like Firefox 8 is out of the picture.
But there may still be Firefox 3.6 users unaware that a newer version is available, this notification is strictly for them. Mozilla wants as many people updating to the latest version as possible, quite understandably.