Imagine the 100's of 1000's of folks who are freaking out around the world after hearing about Rage and can't get to Coachella - me being one of them. If anyone from Coachella is reading these posts, please put this concert on DVD. They will sell like wildfire! I'm just so bummed I can't go so a DVD would be of some consolation.
I would say it is certainly being taped. When we will see the footage, how much, and in what DVD package remains a mystery. The first "Coachella Movie" only had 1 song from each of the artists it selected from the 1999-2004 festival. (20 something in all).
Best case scenario: the Pixies sold a limited edition cd on the festival grounds through an instant CD company in the hours after their set in 2004, and 3-5 complete songs from Coachella were featured on a DVD called The Pixies Sell Out which was released in 2005 after their reunion tour.
I would remind you that RATM released a DVD called "Live from Mexico City", a complete concert that has been available for years.
And what are the odds the Coachella RATM reunion is truly a one-off gig? don't bet on it ;-)