According to this Blizzard forum post The real money AH has been delayed beyond the May timeframe, they did not give an eta.
So blizzard, how about you let us play offline now? I was totally fine with always online until my game actually started lagging. I don't really see any legitimate reason to not let us.
I'm actually kind of bummed out, I had a goal of raising 20$ and buy Warcraft 3 entirely with Diablo money.