At the recent Maker Faire in Washington, DC, I asked the Raspberry Pi guy about the DSI display and he said that it is coming soon, but he didn't have specifics. The delay appears to be the complexity of getting it cleared for EMI. They have a ton of them ready to go once they are approved, apparently.

He did have one of the AstroPi boards, which looks like a fun thing to play with and will be generally available at some point.