it says on that cover in small print "Mock game cover design by an artist at Yazstudios.com " which is no longer a working web page... I think that should tell you something.. and blizzard north wouldnt trust their property to a japanese company... not to mention that cover uses a 2001 blizzard logo
that said, dont hold your breath on d3 being developed yet
As Satsujin said, Blizzard would in no way allow one of theirpremier titles to be worked on oustide of its studios over here. Furthermore, Blizzard prides itself on working on only a couple (if not only one) projects at a time before moving onto another one... and they are still well into development on Starcraft Ghost and maintaining WoW. If Diablo 3 begins getting the treatment, Blizzard will post news right on its website.
I hope they do get around to #3, but I'd much rather get a worthy follow-up to the Starcraft series, and not in terms of an FPS.
All rumor and wishful thinking. Ghost and WoW maintenance are the only active projects according to Blizzard support, as mentioned earlier (not sure why people read the tail end of the chain and not pick up on these things from before). They may have something to announce in terms of upcoming projects at Blizzcon... but I highly doubt they're "two months" into development as of yet without any mention of it on the Blizzard website.