It's a really weird time of day for Amazon North America to end stuff (normally they apply/expire sale prices and the lot a little after midnight Pacific Time) and I personally suspect more glitching of the sort experienced over the weekend rather than a deliberate premature ending.
But I doubt it's likely to get fixed, if that's what it is, by tomorrow.
Incidentally, I can still see exactly four non-PD/permapromo freebies from the sale
using this link, if anyone wants to try grabbing them.