You're looking a little too far ahead, I reckon. I'm eyeing the same dates and destinations, planning to travel up to Birmingham by train to catch BHX-SGN-BHX to get two badges. There's little point in tracking prices at this point of time because QR usually releases promotions monthly, from 3 months up to a month prior to departure in my experience.
And to prove your point, here's another promo !!
Spotted by Antuning.
http://www.flyertalk.com/forum/premi...biz-promo.html
AMS is in the second badge list and the dates are good for 1st & second badge earning period so can be combined with a first badge destination to get you both those badges.
For example AMS-JNB-AMS can earn you both badges at this sale fare.