Man it is really disappointing to hear Rob Pardo of all people say this. I think it's a bit disingenuous, there is a very healthy market for singleplayer games but publishers are absolutely ravenous and wasteful so they want increasing amounts of revenue with numerous ways to monetize the consumer with little risk. They have built these monstrous companies where the shareholder comes before any other consideration and become utterly dependent on expensive marketing for success.
Only in this fucked up industry could someone sell 10 million copies of Diablo 3 and then say singleplayer games are in trouble. This really sucks, it likely means no more SP Diablo or Warcraft.
Preorder a seasons pass and have a chance to unlock a preorder reward! Buy a hat for your pet to battle in a virtual arena! Gaming is such a fucked up business these days.