Team.
The XD9 will read ALL current KETRON style formats of previous arranger products (since it does include all current drum loops plus more); however, the X1/SD1 will not read XD9 styles.
ALL new styles included within the XD9 (plus the additional 25 bonus patterns) will be available for the X1 and the SD1 as independent style and sound disks. EG the new Salsero style found on the XD9 can be obtained if you purchase the same style from your local dealer/distributor for the X1/SD1 keyboard (this will come with the new sounds and drum loops for that style included). Due to more loops and voices/sounds on the XD9, reverse compatibility isn't practical - hence the new styles and matching sounds disks for the SD1 and X-series.
Hope this helps!
Thanks,
AJ