> #1 Only DL mid tier/upper tier FFs can buy a membership (membership proper (not CC access)) and the annual fee is being significantly increased.

This change is kind of interesting to me, since one would imagine that paid members who aren't high level frequent flyers would be amongst the most profitable members of SkyClubs - they can't use the clubs that often since they're (on average) not flying all that much.

All this said, I don't think it's likely UA or AA change anything (other than maybe raising their membership fees); they haven't seen anywhere close to the same overcrowding issues, and having dedicated premium lounges (FL/PL) for premium travel means that even crowded ACs/UCs doesn't hurt their brand for premium flying.