Aw crap, why do I have the feeling they will soon be taking what little money I actually have... again!

I've concluded the publisher.
Atari/GT Interactive/Infogrames

Source? Or have you deduced it?

No source, just what evidence I've compiled, and a hunch. :P

So what is this evidence you speak of? I want to know, or do you feel like keeping it to yourself?

Let's compile the evidence (if you can call it that):
GOG has stated it is quite a big publisher.
GOG already sells many games that are somehow affiliated to Atari/GT/Info.
The tweet:
marty_k - Tomorrow, GOG.com goes wild with.... sorry can't say; in the meantime have some fun with Cannon Fodder :) http://is.gd/oQ3b
"Goes wild". I had a hard time debating whether this was a clue or not, but I'm assuming it is. If it IS a clue, let's narrow down some games with "goes wild" in it.
(hardly any). But, Rollercoaster Tycoon 3 has an expansion called "Wild!" Published by Atari.
Atari is a huge name, and waiting for GDC to announce a new publisher is a rather steep thing to do. We can get many, many, many games if it were Atari.
I know, the evidence isn't clear or conclusive, but that's what I got from it.

Well, we will see quite soon.
But another thing that could perhaps point to Atari is that they published the Witcher in a substantial part of the world. So Atari and CD Project already have a formal relation.

I think it's bethesda, i had a hunch or something before.

Atari... Well maybe that for 5.99$ Atari will finally manage to convince somebody to buy the latest Alone in the Dark :-)

I'll hazard 2 guesses: LucasArts (because I think the supposed "wild" hint is a red herring) or Atari.
BJ

i don't think wild was a hint at all.

Glad you agree. Maybe I should have called it a so-called hint or something to that extent.
BJ

Even if it was the only way to get the thief series on GOG?

I wouldn't dare taint the Thief series with the latest AITD releases.