717 consolidated to ATL.

Not likely for a while. They're adding lots of new hires to DTW and still pulling planes out of storage and putting them back into service.

7ER out of SEA and opening 320 SEA or 330 SLC...

That's what I thought about the MDs and 7ER, but...
I'm guessing that's what will happen, what's your guess?

That’s going to be no impediment to Crew Resources. They can do the displacement and have them all trained after the summer. Specially if they have 365 days to plan for it.

Again, that assumes that the fleet will be shrinking before summer 2023. Given the pace of demand we will need that lift, and won't have enough new orders to both keep up with growth and replace a sizeable number of 717s in that short of a time. Someone mentioned SEA 7ER as a possibility, and that may be but then again they just added the Chinese visa requirement to that category, implying that they have future plans for that category (not that that really means anything). Admittedly, their list of options to displace from is rapidly shrinking. I mean they're probably decades away from closing any 320 or 737 base, and the 220 is still ramping up. That leaves the 7ER and 717. ATL 717 will be the last hill to die on, probably same with the 7ER years down the road as well. So basically that leaves just a handful of 7ER domiciles and DTW 717. Who knows, maybe after all this talk they actually will decide to not do a 365 bid next year...

Displacements means 2. (plural) One less CA and FO in any base or equipment would work.

This plus maybe LAX7ER.

I understand that, but every narrow body category will be shrinking by attrition anyways unless they add more people. Say a category has 100 pilots, and they post a displacement for 2. And then 10 pilots bid out. Can they still backfill back up to 98 and have that count as a displacement for the purposes of a 365 day bid?

Since you answered with a question, YES, they can absolutely do that. Unless the arbitrator decides in our favor.