If your next qtr is 12 Sep, it means currently this 12 July will be ur first month of the next qtr . Only the first of 3 mths, and if I am not wrong , your next qtr will fall into the revised cashback terms of 3.33% max, meaning not $300 anymore, only $200 if u spend 2k for next 3 statements.
i would forgo it , in view of these 2 conditions ( lower rebate as well as being only the first month of your qtr )
and I am guessing nobody in this forum would be able to tell u correctly your exact chance of successful appeal 3 months later.