BG1 saved before the final boss. I expect the same here (nowhere near to check).
As Crash stated, they're working mostly on fixes and 'free content' now... but with the success of Original Sin I do hope for a proper expansion down the line, yes.
For what I wish for... well, more storycontent and stuff. Can't really say any mechanical upgrades come to mind that I want. I assume many people would want day/night cycles, but I just think adding that while nice, would reduce the size of a potential x-pack greatly (since all devtime needs to be in updating the old areas too for this, and thus leaves less time working on the new stuff).
Although I do always like if expansions also spice up the original campaign, I think other ways like a few new quests, resolutions and stuff suit me better than day/night.
My 2 cents.
