Well after many Diablo fans came away from Blizzcon disheartened and overly unimpressed with Blizzard, many are still asking WHEN not IF Diablo 3 will come out? I'm one of those people and I'm not to sure what is going to happen.
There haven't been many pointers at a new Diablo game but the ones there have been have been pretty big, these being:-
1 - Legendary Pictures, "accidentally," placed an in development, "Diablo," movie on their home page. They have made no comment on this and quickly took it down.
2 - New Diablo artwork has been appearing on the Blizzard website and on the Blizzcon banner.
3 - A new, 40 man strong development team codenamed, "Team 3," are working on an as yet unannounced game title.
All of that said however, Blizzard are one of the single most annoying companies when it comes to gaming titles and releases. Their view that, "it will be released when it is ready," has been proven time and time again and also that if they don't like it, they will scrap it (see: Starcraft Ghost).
So we have a team of 40 devs working on a new title. It could be Diablo 3 or it could be an entirely new franchise. At the end of the day however, we do know that they are intending on working on all 3 franchises in the future. It is almost a decade between Starcraft 1 and 2.
Perhaps they are going to make people wait 3-4 more years for the release of the sequel to one of the biggest RPG games of all time.