To lay all of the Internet rumors to rest, I contacted WOLF ammunition by email to ask if they planned on producing 5.7x28mm ammunition in the foreseeable future. This is their reply, dated January 5th, 2009:
There are no plans on producing this caliber in the foreseeable future.
There you have it folks. The future of cheaper 5.7x28mm ammo for your P90 or FsN is bleak.