Well, let's look at the facts and rumours;
- 110 airframes on order that could replace every A320 in the Jetstar group and still have a surplus of 40 aircraft.
- No deferment or cancellation of any of those orders
Well those are closer to rumours than facts. (Or perhaps we should call them "alternative facts" these days)
-The order is for 99 aircraft, not 110.
-According to the JQ website they have a current group fleet of 107 A320/321's. So there would be no surplus if the entire order were used as replacement airframes.
Jetstar Group fleet | Jetstar
-The A320 order has been repeatedly deferred. It was deferred in February this year:
Qantas to defer A320neo deliveries, reports drop in first half profit | Australian Aviation and in 2014:
Jetstar delays Airbus orders until 2022 | afr.com
So I'd say any replacement of the approximately 70 Qantas 737's will be a new order in itself and need not necessarily be linked to the existing JQ order.
To throw another rumour out there though; apparently QF still have cash tied up with Airbus for A380 deposits for the remaining aircraft they have no intention of ever receiving. Moving this money into a QF A320 order could help increase the appeal of the Airbus product over the 737MAX.