With an east coast narrow body command in QF going close to 20 years I suspect we are a very long time away from that situation morno. West coast narrow body commands currently sit about 16 years.
Of course if you want a 737 F/O slot in PER you can have that on day 2 of joining.
That all could change too if we rapidly increase the size of the 787 fleet without retiring aircraft but it’s still not going to see the situation you describe. More likely to struggle to get people to take F/O slots but that’s more related to pay and conditions than individual pilot skill level.