In the new products page on dailymtg.com, the intro pack decks minus new Magic 2015 cards are listed.
The return of convoke was known, but these cards also hint at a theme of Defender/Walls in the set. It is interesting to note that this is the first time a returning core set mechanic included reprints that had the mechanic.
Also listed on the new site is a partial decklist for the Magic 2015 clash packs. New Magic 2015 cards are not listed, but the notable cards listed include Nykthos, Shrine to Nyx, Prognostic Sphinx and Temple of Mystery.