GOG uses DOSBox, but what about when DOSBox gets updated, do they update the old releases with a more stable version of DOSBox? Or do they use a certain version for all their games?

Apparently games added after DOSBox 0.73 release already use the newer version. The games added before it still use the 0.72 version (Stonekeep DOSBox has apparently been updated but I think I read new version fixed some problem with it).
GOG games that use DOSBox in DOSBox Wiki

As I recall a blue poster did say that they will go back and update earlier games... but that it takes a lot of resources (man power time) to do so and as such will take a while to do so...

Weird. I was just thinking about this same thing.
I was thinking it'd be cool if there was some kind of central GOG installer/launcher.
(not too much like steam, before everyone gets their pants in a twist).
It'd just be a simple launcher, that listed all the games stored in your GOG folder, and showed you any updates to their status (patches, support tickets, etc..)
It could also allow GOG to use one central copy of dosbox, which would then be easy to update from within the launcher. Rather than having a copy of dosbox for EACH game.
(of course there might have to be exceptions for games that need a specific version, but that could be handled in the launcher too. )
PS/ Is it a simple task to update the dosbox verison of a game i have installed? Just overwrite? Or is it more tricky?

Just overwrite. You'll need DOSBox.exe, SDL.DLL and SDL_net.dll.

Considering they'll probably need to update all their installers sometime after Windows 7 hits the stores, they'll most likely wait until then and do both at the same time.

Unlikely. All the GOG games I've tried on Win 7 so far have worked without any changes. Win 7 is not too different from Vista, so if they work on Vista, they should be fine on Win 7.

That's it.

I've seen several topics from people running into problems running GOG games in Windows 7 so it may not be so straightforward as it should be. Then again it is RC version of Windows and the broblem might be divers, codecs or anything else for that matter. We'll have to wait and see.

Oh and if one of the games doesn't work after updating. I'd like to know about it.

Thanks!!
.... and i'll try to let you know if one doesn't work Qbix.

Yeah, I was just trying to install DOSBox for Arena and Daggerfall, and it's a pain. I wish the guys at GOG could have had their way with them. Even though Arena and Daggerfall are free, I'd be willing to pay for decent working non-hassle versions.
But yeah, I noticed that the latest version was somewhat recent and was wondering how GOG handled that sort of update.

When GOG does update a game, they release a whole new download package for it, at least that's what they have done so far. To date, they have not released anything like a patch to fix or add things to the games, just full downloads of the updated game.

Try D-fend reloaded. It is a pretty nice front end for dosbox, and it has premade profiles for a lot of games. If you don't like comman lines it'll probably really help out.

For reference, D-Fend Reloaded is available right here.
The only bothersome thing with Daggerfall--with or without D-Fend--is getting it to recognise the mounted CD folder; Daggerfall demands that the CD is labelled "Daggerfall" and won't work otherwise.