To me its all in the game, RIGOL could have easily closed the loop hole, but they did not. In fact I suspect that RIGOL helped the guys that needed to unlock the scopes with hints and private keys, all too boost the sales. For example the DS1000Z license system was also suddenly unleashed with the help of an anonymous source. That's now almost 2 years ago.
I've wondered that too, perhaps Rigol doesn't mind unlocking, even secretly likes it, since it increases the desirability of the scope. Really, 300 MHz 2 GSa/s for under $900 is pretty kickass. Business customers aren't going to unlock them, and they'll want to keep the warranty, whereas hackability quite possibly increases overall revenue coming from us mere mortals. I agree about corporations, some of them are pretty awful.
I'm not sure when the DS2000 came out, but the DS2000A hasn't been out that long, although it didn't really seem like much of an upgrade, 50ohm input, maybe some firmware fixes. Did they actually redo the front end to get that extra 100Mhz, or was it more like swap out a component or two? Seems to me they are basically trying to squeeze a bit more life out of an existing platform before moving on (and the 4000 series is getting old too). I'm just trying to decide how long I should wait to purchase one, with lucky timing, there's the possibly of some killer deals to be had.