Has an "end of life for gtk2" been announced?
 

I have not been able to ascertain whether an "end of life" for gtk2 has ever been announced. I am just curious.

gtk-1.x & gtk-2.x coexisted for quite a while in development terms, because each was required by the range of apps using gtk.

I imagine it will be even longer this time with gtk-2.x coexisting alongside gtk-3.x. It isn't until these have migrated to gtk-3.x that gtk-2.x will fade away. It was very similar with versions of Qt - qt-3.x & qt-4.x.

And besides, lots of programmers think gtk3 is a slow-motion train crash,

it's an interesting question, but if you're not a developer, it is absolutely pointless to worry about it.
i use gtk2 and NO gtk3, i will continue to do so as long as possible.
whenever it's not possible anymore (or will require unrelated drawbacks, like using outdated software), i will then start using something else.
fortunately i'm using a distro that makes these kind of choices possible.