http://www.theregister.co.uk/2010/02/09/firefox_tiger_10_4_support_to_end/

I guess I'll be maintaining a Mozilla fork for Tiger too when 1.9.2 (3.6) goes EOL, though I'd likely maintain it based on Camino since I don't use Firefox much.

At least Firefox X11 would probably still build on Tiger, even though that would be much less convenient to use.

Well, it was bound to happen sooner or later.