I think that that we are speculating too much.

I don't think that the new sounds/Styles have no been release because hardware issues. DonM and others are testing them and have no report any issues.
No sure is if there software issues either. No body that I know that have the combination OS4a/new sounds/new styles have reported problems. No issues either with styles from other keyboards (SD5 and Midjay).
Bugs ? . For sure. The only software with-out bugs is the one that has been release yet.
My feeling is that Ketron is adding additional content and testing then very fully. remember that that Ketron is no a big company like Yamaha, Roland or Korg. Probably resources are at premium.
My main critical issue is the way that Ketron keep in touch with the customer base. No relation can work with out contact. It will only will take Ketron to design a person to be point of contact for customer worries and concerns.