As you might know, symfony 1.4 "end of maintenance" date is coming up in November 2012. Recently, Tom Boutell asked for some clarification about this fateful date on the symfony dev mailing-list. As he is probably not the only one to look for some answers to his questions, this post summarizes my answer and, hopefully, it will serve as a reference for any future questions on the same topic.
First, be reassured that the whole symfony 1 "infrastructure" won't be shut down at the end of November: the symfony-project.org website will stay online; the SVN server and the plugin repository will stay online; the documentation will stay online. Trac will probably be put in read-only mode (the wiki) or shut down (the ticketing system).
But what about the code? What about people willing to support symfony 1.4 in the future? What about all the websites that use symfony 1.4? What can you say to your customers?
The symfony 1.4 code is very stable. I'm still actively monitoring the new tickets, but there isn't that many bugs that can be fixed as part of the maintenance. Many problems are just not fixable without introducing some kind of backward compatibility breaks. And as a matter of fact, I had to revert some changes in the last few months because so many people are relying on the current behavior, even if it is not necessarily the good or the expected one. Still, we are publishing new releases from time to time, but all fixes are very minor ones, and we have less and less of them.
The only valid concerns are about forward compatibility with future versions of PHP and the possible security issues. For those problems, and if the community is willing to help, I will happily accept patches and package new releases on a case by case basis.