We don't yet know if it will be quite that extreme, but the reason I'm reading this thread -- and now adding a data point -- is a completely unexpected Gold renewal in my family.

The member in question ended her first year with Gold status on fewer than 800 TPs. She racked up 400+ TPs in the week after 8 August to start her new collection year, and will reach 1,500 TPs before October ends, but should still by rights have dropped to Silver this past weekend. She didn't and on checking the BAEC website saw that a Gold renewal pack was sent out on 14 August (she hasn't seen it because she's been travelling).