I'm highly sceptical.
Ignoring the auction house for a second, Blizzard makes money once though a large up front sale, and then has no monthly fee. The game is played entirely on online servers with no single player however.
That means Blizzard makes the most money from a customer who plays though the game once (or not at all) and then doesn't play again.
This philosophy seems to be present throughout the games design which, as far as I can tell, is tailored for minimum re-playability and maximising the fun you get on your first play through. Even the auction house itself helps this design goal when matched against their other design decisions.
This kind of design isn't conducive to long term success with the auction house.
I believe that the auction house is primarily designed to kill 3rd party item sales, which it absolutely does, albeit in a way I find personally distasteful. While I'm sure it will be a non-trivial revenue stream, I don't think it will be anything like what WoW subscriptions were.
Disclosure: I work for a company making a competing action RPG.