I hope this isn't true, because if it is, the platform will be stillborn. The whole pitch of WP8 is "it's like WP7 but better." If it doesn't properly run key WP7 apps, that hurts the pitch.
If anything, the new SDK is needed now more than ever. If WP7 apps don't work well, they'll need to be updated, and there ain't no updatin' without a current SDK...