I don't think an anniversary show or two for Purple is entirely out of the question... I think Chester has said it's his favorite STP album, and since Linkin Park will be working on new material next year I imagine the only reason CheSTP will be performing will be to play old material. So maybe a couple festival shows playing Purple material in summer of 2014 is possible...
As for what would have happened with Scott, I imagine the exact same thing that happened with Core would have happened with Purple... They would have talked about playing the album in it's entirety; and then when it came time if Scott didn't display the ability to play Kitchenware, Unglued, Army Ants and Pretty Penny night after night; they would have just played a greatest hits set instead.
As for releases/re-releases of old material, I've given up entirely. An official release of the Centrum show from 1994 would be the holy grail for me, but it just doesn't seem to be in the cards.