So... will this Game get Boring too Quickly?

Saying kag dying out in a sense is too bias, not judging from my perspective but i think Kag is just losing the other's interest.
Depends on situations, for some, kag is really addictive and fun at first but as times goes on and on when they doesn't feel belong to the game anymore, they leave. For some, their pc can't afford great games to run on, and kag (or other indie games) are their best choice to stick with.
Gaming industries these days are growing, and there are many different games on different favors. Not all games are bad, but not all games are perfect either, it depends on how the devs satisfy the players' need. You can't just say kag dies simply because the game is not always 24/7. Personally my self, I still think kag is a great game and would be in my list of my fav games, every time i had a bad competitive match in cs go, i play kag to make myself feel better :)
In the case of players slowly diminishing, it's probably up to the devs to make a better change to the game or even advertise the game globally in order to gain themselves profits. Kag is not easy to find if you don't see it through advertisement, usually i found kag through finding some website that said ''top ten games that are like minecraft'' a very long time ago. Nowadays, people rarely search for such categories.

 

That's already been like a year KAG updates are being more and more handled by the modding community. No, Geti hasn't stopped working on it, yes, they're principally working on Trench Run for now. And what would be the problem in that? They've been working on KAG for years now and Verra, Skinney, norill and a couple others have been working a lot on awesome features.
AFIK, KAG and TR engines are on the same branch which implies a KAG engine update will apply to the TR engine, and the reverse.