I'd say crewing will be there biggest problem considering the anticipated competition for pilots this year.
It's all well and good to bring forward deliveries as they have, but they'll be parked for a while if they can't crew them. Expansion will come to a grinding halt.
Besides, why would you go to Tiger when you could just as easily go to Jetstar on better terms and conditions?
On a side, i note with interest that the QF propaganda machine has gone very quiet re TT.