I'm almost done with Baldur's Gate, I think. I actually finished the game completely unawares the other night. It turns out that Sarevok in the Undercity's Temple of Bhaal is the final encounter. I guess I should have realized that before killing him and seeing the message that my savegame was ready for export to Baldur's Gate II.
I re-loaded to a save just outside that fight and now I'm going around cleaning up all the sidequests and doing the expansion content. I would guess I have another 5-10 hours left with the game. The only things remaining to be done that I am aware of are a quest to get some sea charts and then find the shipwreck of Balduran, the founder of the city of Baldur's Gate, and then to delve into Durlag's Tower, which I think is the hardest dungeon in the game. I guess I could be surprised by a huge new quest chain that pops out of either of those, who can tell.
I've done every other major sidequest, as far as I know. I even have a few maguffins in my inventory whose proper owners I don't know where to find. I'll get through all of the aforementioned real content and then consult a wiki on these few odds and ends before going back to kill Sarevok--on the record, this time.
I'm not sure what I'll play after Baldur's Gate. I think I'll need a bit of a palate cleanser before moving on to the sequel. I did just get a new GTX 970 video card, as well, and I'll want to put it through its paces.