Because Activision pretty much threw out what was going to be DJ Hero 3 out the window for the "hiatus". Not sure when, not sure how, but FreeStyleGames has moved on from DJ Hero...
....even though they REALLY WANT TO make a DJ Hero 3, they are in MAD debt/financial problems. Yes they are still alive but that's because they somehow made a deal with Activision to keep them alive for just a bit longer. They are making a new game, but it's not the one you think it is.
It's SiNG (working title) for the Wii U.