Is 2.0 like a big patch that will be released on the 29th of September that completely overhauls the game and will be installable to any version of the game you have (retail, GOG, Steam whatever) using the "update" button in the menu, or is it like a new version of the game, like the first Witcher's enhanced edition?

I am thinking of buying the game (a retail version actually), but the description on Steam really worried me that if I buy it in retail, I'll end up with an older version like the first Witcher's red-cover edition, or something like that.

It's a patch.