I'm guessing yes, and the business model is to get their foot in the door with DAW users, then make their money with the ADpaks. I was happy with Session Drummer, I was looking at the ChocolateCake drums, then I tried Addictive Drums and they got me. I'm just waiting to see a special on the ADpaks and they will get my money.
Although they will continue supporting Addictive Drums 1, I doubt you'd be able to download it after the 13/5 , and as such, if registering is the same as buying (and I can upgrade to AD2 for free as I purchased on the 31/3) effectively after 13/5 you actually get AD2 with X3, which is a nice little bonus for Cake.