Yes it does, i just upgraded to an XL a few weeks ago. Everything is there, play coins, play and step data. You do have to download apps & games again, but it's all saved within the system, it acknowledges what you bought so you're able to download it again
That'd be awesome. Sorry about the change, but I'm fairly certain I'll be using the XL more than the original now, and with the AC:NL release on the horizon, I figured I should start adding people on this one instead.