This is truly exciting news, because I love both of these guys' playing. Certainly the Mick Taylor era was the hands-down best era for the Stones. It will be interesting to see how he fits in all these years later.
Taylor's role was always to tastefully noodle throughout the band's repertoire live. They even gave him two solos in some songs, such as Love In Vain (video below).
I hope he gets to play at least a couple of songs per night.
By the way, I have DVR'd the HBO Stones bio Crossfire Hurricane and hope to check it out this weekend. I'll let you all know what I think.