This might not be 100% accurate but I believe what happened was the original Alteil 1 in Japan got to be so unbalanced that they eventually decided to essentially start over and thus created Alteil 2, which is the same game, but with different cards. By different cards, I mean that its like they just continued in sets, but separated all the new ones from Alteil 1. I think that's really the main difference.
In other words, as long as the GM's can keep up with the game balance, we aren't going to ever get Alteil 2 over here.. except for the new features that are present in Alteil 2 JP, which we'll just get in our Alteil. Once the Alteil 1 sets run out, I believe the GM's plan to move right on to Alteil 2 sets in our version without the separation.
Please someone correct me if i'm wrong.. this is just me remembering what i've gathered over time. I don't pay much attention to Alteil JP