Well my dashboard still has a deadline for 2-4-1 voucher of 4 November. (which I will unfortunately comfortably make!). Bit harsh to be changing the goal posts within the current earning year. At least give 12 months notice (as BA have with threshold changes).
Personally, given less travel for work/reimbursement for personal CC spend, plus the number of major outgoings (energy bills etc) who don't take Amex, 15k might be a bit steep. Amex need to work much harder on broadening their acceptance if they are increasing spend thresholds.