Agreed - I think most programming language communities have settled on one major framework (though there are plenty of other smaller ones) and they've survived.
Oh I agree - 15 years ago picking a web framework would have been much more difficult - for web frameworks now though I think that using the most popular choice should be quite safe.
Symfony is actually more like several different frameworks under the same name. Some of our projects are stuck with Symfony 1 and upgrading them to the latest version is aking to switching the frameworks because they have almost nothing in common.
Spring: June 2003
Rails: August 2004
Django: July 2005
Symfony: October 2005