After 10 years with Blizzard, Diablo 3's previous Game Director Jay Wilson left the company last month in order to focus on his writing career. While it was never confirmed whether the community backlash over Diablo 3's once lacking features played any part in his retirement, I can certainly guarantee you that it wasn't a pleasant thing to endure, but such is the life of a Game Director behind one of Blizzard's biggest franchises.
With Jay Wilson now gone from Blizzard, there is apparently a need for another experienced Game Director to step up to the plate and "lead the Diablo series into the future", as noted on the recently updated job posting on Blizzard's official website. While that alone might not be significant enough, the fact that they are hiring a Game Director for a new and unannounced Diablo project is quite intriguing indeed. Here's the brief quote describing the position:
"Blizzard Entertainment is seeking a game director with outstanding communications skills, proven experience in creative direction, strong ability in system design, and a stellar track record of shipping AAA games to lead the Diablo series into the future."
As of right now there is literally zero information available on this project, so while I would love to offer you something more concrete, there is simply nothing out there. What it could mean, however, is that Blizzard is working on a second expansion for Diablo 3 (quite likely), or even an entirely new game set in the Diablo universe as the job posting cites the need for Game Directors with experience in "online games, action games, and role-playing games". I have my doubts the second theory is true since all of that can be used to describe Diablo 3 as well, but its certainly an interesting little topic to speculate upon.
If any more information pops up I'll make sure to update you, though I highly doubt we'll see anything for at least another year.