I saw that some of these games are coming to Steam and that they're doing some enhancements. Any chance they'll be available here with those enhancements as well?

If you want an enhanced version, try the Goldbox Companion. It's a third-party utility that functions mostly as a cheat engine, but it also adds some quality of life features.

Where did you read they are enhanced? Everything I've seen so far looks like they'll be the same. (Not saying you're wrong. I just want to know if this is the same as we have on GoG or not, so a source is appreciated).

From what I've heard they're not enhanced at all. For Steam enhanced probably means "comes with DOSBox".

Doesn't GOG hold the rights to these AD&D games? So any upgrade would probably be available here as well.

Now the responsible for the games are a company named SNEG, it has some kind of relatioship or conection with GOG, The Steam versions are not exactly enhanced versions. They are just reedited versions bundled with the Gold Box Companion and the All seeying eye free apps and some kind of launcher to select the games.
BUt The collections are exactly the same as in GOG versions.

The matter is if those versions are going to be released here eentually.