Not for sale. If you already bought them, there are still in your library, but you can't buy them anymore.

epic exclusivity wont last forever. i mean as a concept, not individually :P
there'll be a crunch. you wait 'n' see; peeps will get sick of it.

Sure about that?
https://store.steampowered.com/app/675260/Batman_The_Enemy_Within__The_Telltale_Series/

What bothers me most is that I have 4 seasons of Walking Dead and expansion but not the Final Season. And after many years I'll be offered to buy whole remastered package again but the original final season game will always be out of reach.

Hopefully.

Not to GOG apparently. Some games are back on Steam but GOG seems to be completely ignored by the new Telltale. Can a blue confirm if any progress is being made to bring these games back to GOG?

Has any effort been made to form contracts with the new Telltale in order to return the games that have returned to Steam already?

I would think an attractive point is that they wouldn't even need to send you the files, the games just need to be relisted after contracts are signed.