Increased system requirements and dependencies (dropped XP and Vista compatibility
, maybe problems with Wine), shortcuts which start Galaxy in the background
and not only the game and maybe more. ;)
I'm afraid that will only be the case for the installer itself and not for the game. Unfortunately Galaxy seems to be implemented in a way that the dll always is loaded, even when no Galaxy functionality is used. But only the future will show. Better download your installers now. ;)
You seem to be mixing up two things (which may be related, but not the same thing):
1. Already now, many GOG game installers have a Galasy DLL included with the game. You can still play the game without Galaxy (installed), but apparently it may cause some "hiccups" like starting Galaxy (when you run the game) if you have Galaxy already installed. This is here and now, the current situation.
2. The announcement from GOG that they are planning to include a Galaxy installer to the offline GOG game installers in the future
. You can then choose whether you let it install Galaxy or just install the game, similarly like already now many GOG game installers offer to install a Foxit PDF reader with the game, so that you have some PDF reader in your machine to read the game manuals.
And yes they have also said that they would offer two different sets of installers for the affected games, one with the optional Galaxy installer embedded, and one without. I personally hope they do not go with this "two sets of installers"-plan as it can potentionally be very bad news for e.g. gogrepo and lgogdownloader users, depending how they implement it. I see it as a silly plan as if they offered two different sets of installers now, one with the Foxit PDF reader, and one without, for each game. For simplicity's sake, just offer one set of offline installers, with or without a Galaxy installer (and hopefully with just a small 2MB stub installer, not the whole 130MB Galaxy installer in each game).
Separate sets of installers should be offered only if the game content itself is different between them (different language versions, OS versions, if one set is a remake and the other is the original version, etc.).
Anyway, I feel they suggested this "two set of installers" approach in the heat of the damage control, just trying to quickly ease the minds of those who were vocally very much against embedding Galaxy installers to the offline installers. I am pretty sure that now that they've been thinking about it more, they probably realize it is not a very good approach for them either (two different sets of installers to be taken care of for the same game, more work for little or no benefit).