Hang on.
You WILL be in the next MEMBERSHIP year after 8th Dec (i.e. 9th and onwards).
HOWEVER, your card expiry will probably be 01/13 or something like that? If so, you should still be able to access lounges, etc until then.
(However, if you are flying business class, then you will get thouse benefits anyway.)
Your TP will reset to 0 after the 8th December (as you enter your new membership year), but you will then to build them up again.
Assuming you are in paid business class (and not a miles redemption booking, etc), you will earn 140 TP for the outbound LHR-JFK.