Well, while reading over at the PS blog about their PS4.
PlayStation Meeting 2013: The Future of Gaming is Here with PlayStation 4 ? PlayStation Blog
I noticed this
A partial initial lineup for PlayStation 4 includes first-party games from Guerilla Games (Killzone: Shadow Fall), Sucker Punch (inFamous Second Son), Evolution Studios (Driveclub), and Japan Studio (Knack), as well as titles from our partners such as Activision/Bungie (Destiny), Blizzard Entertainment (Diablo III), Capcom (Deep Down), and Ubisoft (Watch_Dogs).
Edit:
Here you go with the announcement!
We can play D3 in 4 player co op mode on a ps3/ and ps4
http://us.battle.net/d3/en/blog/8717...%AE4-2-20-2013