The OP says:
Originally Posted by
agentred
(I don't plan to travel as much next year as I did this year).
and
Originally Posted by
agentred
should find it easy to earn enough miles to be gold in 2018.
where this latter must be read as starting from an opening level miles balance of 29800 [so, requiring only 10,200 miles in 2017]
Hence, there are no "excess miles" to move to 2017, and for the sake of 200 extra miles in the next 6 weeks, Gold into 2018 would be lost.