According to Mozilla there are some 12 million Firefox 3.5 users out there surfing the interwebz, but Mozilla now needs them to upgrade to a more recent release. And Mozilla has drawn up plans on how to accomplish this mass move.
Firefox 3.5 users have two options. Mozilla would prefer that they upgrade to the latest Firefox 4.0.1 release, bringing them bang up to date. Alternatively, if they don't want to go to Firefox 4 (perhaps because a plugin isn't supported) then Firefox 3.6.x (currently 3.6.17, with 3.6.18 planned for release June 21st).
So, how will Mozilla deal with those still using Firefox 3.5?
Well, starting with those who have automatic updates enabled, Mozilla will push Firefox 3.6.18 to them after it has been released. Why 3.6.x as opposed to 4.0.x? Because Mozilla considers 3.6.x to be the security upgrade for Firefox 3.5 users.
However, before that happens all Firefox 3.5 will be given warnings that they are running an out of date browser on the default Google search page.
Firefox 3.5 users will have also been warned via the firstrun messaging mechanism built into the browser. Mozilla can also send pop-ups to Firefox 3.5 users informing them of the end of life status of their browser.
So, while I doubt that many readers here will still be using Firefox 3.5 (I just checked ... that stats back up that very few of you are using Firefox 3.5 or older), chances are that you someone who is running an older version ... tell them what they are missing ... before Mozilla has to!