Having a new album is important for a lot of acts but even without a new album both acts would sell out the Greek Theater which is over half the capacity of TI. More importantly, both are touring this summer in Europe with open dates for the fall. If APE could book them, I would think/hope they would.
Well if we are going with bands who have not released a album in a while to headline Saturday I think Kraftwerk is in the cards. I know they played Three shows at the Fox (I was at the second one) but I wouldn't be surprised to see them pop back up for TI, I feel like it would be a good outlet for their 3D tour right now.