The Product page is very clear that this is an EZdrummer 2 EZX. EZX:s released from now on can be loaded in EZdrummer 2 and Superior Drummer 3 (all previously released EZX:s can be loaded in both).
I can't speak for what will happen or not but not many EZX:s have a "big brother" SDX release and the last time it happened, they were announced at the same time.
BR,
John