I hope we'll just have re-download the game and that they'll already have the expansions installed and set up because I wouldn't know where to begin installing expansions for DOS games.
That would be the most sensible thing. In fact, I'd expect exactly that. In the past, GOG has completely replaced their installers when they realized some settings needed to be tweaked still after the initial launch of a few games that they released. It just makes sense that they'd do the same if they add something like an expansion.
Anyway, until it's officially confirmed I'll hold back my excitement. It certainly would be nice if it did happen.
I missing anything?
Only the most notable one: Alpha Centauri's Alien Crossfire