Agree the retro scheme looks great, albeit sadly (like Aer Lingus) they didn't go bare metal for the lower half (or the engines)
Compare to this SP pic:
VH-EAA Boeing 747SP
ANCDU,
With the 320neo performance versus 737MAX, and potential oversupply for Jetstar (particularly if Asia continues to stay with static aircraft numbers and Hong Kong isn't approved) would not be surprised to see a 320 in Red.
That said oldest 738 is 2002 delivery (the order AA cancelled after 9/11) and an internal refurb project begins next year, so suspect it will be a while before they are replaced.