It’s been very stable with all updates in the last year. The lass issue was when apple moved to https which is why the certificate is now needed and when that issue occurred the plexconnect team and community had a working solution within a day, and it was refined over the next week to be what we have now.
But as you said its an unknown what apple is planning, but some people have been able to use plexconnect on the latest ATV beta firmware on the atv3
Simply not update the apple TV. Update bring basically nothing to it; the only valuable update I can imagine is an app store, and that would fix the need for plex connect.
Wait for the fall for AndroidTV boxes which I believe will be much nicer boxes than what ATV is at this point. Unless you use airplay a lot I think it would be the best thing to do. I know my own apple TV 3 won’t see much use one I get my hands on one of those. Search YouTube for Google IO 2014 android TV to see for yourself.