So in turn, what if you made a reservation that lapped the UY?
when you book this originally, you'd need MS to make or link the reservation upfront, BTW. at this point, i don't think you can make an online reservation that crosses or laps UYs.
...Say Nov 28-Dec 5th and then had to cancel 60 days out. Would the December points be usable the entire UY, but you'd lose the November points because you can't bank them?
right. the pts used to book nov 28, 29 and 30 would drop back into
that UY (for a dec UY and a nov 2014 stay, that would mean your 2013 UY.) so if you canceled after the banking window closed on july 31, you'd have to find a way to book another stay that was completed before nov 30 and use that (for yourself, your family or you could rent the stay) or it might be easier to try to rent those 3 nights as booked (if it's difficult to find other availability on short notice.) but your options would be very limited.
for the "current" pts used to book dec nights (for a dec 2014 stay, that would be in your 2014 UY so your 2014 pts would be current), you would have the option to bank them through july 31, 2015 or you could still use them in that UY for a stay through nov 30, 2015.
for any banked or borrowed pts used to book dec nights, you would need to use them in that UY for a stay through nov 30, 2015 (as you can only move pts one time with banking or borrowing, and after that, they are stuck in their new UY). but at least you'd still have more time to book a different stay or find another way to use the pts.