Bummer indeed, but to your question. Yes, they generally honor all previously made reservations at the booked rate, however, once out of the HHonors program, you will not earn any points.

Sometimes they even go beyond what's required. When the Hilton in Paris near the Etoile de-flagged, they still honored my HHD benefits with EL access and breakfast for 2 rooms for 4 nights, which was really unexpected, and much appreciated.