Will be interesting to see what they do with Jaheria. In the books Jaheria dies and cannot be resurrected, not even by the (potential) new god of murder. If she's in the game it will mean that the video games are cannon and not the novels.
Just from what I've learned here and in Bladedancer's mega thread, those novelizations sounded pretty incongruous to the games, I think even the first book doesn't even jibe with the beginning of Baldur's Gate II. It's the "Murder in Baldur's Gate" adventure that I think they'll be pulling from the most, and the comics. I don't really know much about either though.
I think the fact that Jaheira is in the sourcebook as a leader of the Harpers indicates that she'll be in the game and not dead. I also think that Jaheira is the person who sent the drow Jhaam and her crew to Grymforge to investigate.
Notice the note that you find on the dead drow at Grymforge, and notice what Murmath, the duergar spider master says. "Had the smell of the surface on them." They weren't Underdark Lolth Drow. They were surface drow.
And the note says that the writer is anxious/concerned about the cult's activities at Grymforge. Jhaam was being sent by the writer to infiltrate and check it out because Jhaam never failed the writer previously. None of that sounds like Underdark Drow to me.
Finally, the note is signed just "J". Who are we constantly running into in the game who are investigating Grymforge and such? Harpers. They were there back in 1372 investigating it, and I'll wager that Jhaam and her crew were Seldarine Drow Harpers also investigating it.
Just a theory, of course, but seems probable to me. If according to the sourcebook Jaheira is a Harper leader, it would certainly fit that she's in Baldur's Gate and she sent drow Harpers to learn more about the cult and the forge.
They also mentions how their eyes weren't red, which is apparently a trait of Lolthsworn (retconned). It's a good way of roping in Jaheria, but also be aware that most of the Harper stuff we find is from when they were investigating Thorm.