Sounds like they are down playing the announcement before it's even been made so dont expect anything amazing.
With Blizzcon back this year they would be crazy to announce anything big outside of that anyway. Either Blizz all stars or some type of Facebook game in my opinion.
I think it's just related to showing actual D3 gameplay footage on the PS3 and possibly letting people try a demo. The wax seal in the email is identical to the wax seal in the D3 in-game cinematic (http://www.youtube.com/watch?v=JID1u9qiMjQ at 01:11).