I don't particularly feel any need for big changes or expectations of a road map. I bought a game, and I played the game. It was a good game, I might play it again, but I'd rather they made another good game I can buy than keep updating the old game. I wondered about expansions, but I don't really see how they would fit in. If they added another long mission in the middle it would feel like you were being distracted from the Absolute quest; and if they add something at the end it would either cheapen the existing victory ("Oh no, it turns out there's an EVEN BIGGER problem"), or it would depend on who you're friends with at the end, and given that I've only played once it's possible that they are doing different things after the main quest depending on what happened.
Before the news that they're not making a sequel I thought that a better option would be another story in the same engine, but given how much writing, level design & animation there is in a game this size, I can't really see them saving much time. It would just be the next Larian game and they might as well do a few years' engine updates too.
As for the difference between BG3 and D&D rules, I think that's more that they altered the rules as they felt better fit their game. There are things you can do in a tabletop game that just can't be done in a video game, and they must have thought the balance worked better with other changes. What I'm saying is, changes to the rules if people want to play with pure 5e rules seems to me to be a better fit for mods than an official patch, assuming such a thing is possible.
I would quite like a character sheet export - like the character sheets you get in the deluxe edition, but including your custom characters and the stats you end up with. I'd also quite like a load of stats of your gameplay, like the number of long rests, number of fights, character deaths, opponents killed, etc. For some reason once I got to Baldur's Gate I was really curious about how many days (i.e. long rests) it had taken me since the nautiloid.
