If US went before ICAO, which was what almost happened a couple years ago, then there would be a lot of disruption...

They'd either have to retrain elders with two years left for fleets where they could bid domestic, or possibly just end up having to pay them WB CA pay to sit out the last two years, depending on CBA language, the language in the law, or maybe just the cost of re-training.

This was a US-only issue.

It's not apparent to me that there's been a change in the position of the US legacies

Regionals, ACMI, bizav were in favor of 67 all along. I think most foreign airlines are in favor, since most of them have perennial pilot shortages

But it's obvious that if ICAO goes first or at the same time then the only remaining downside for the legacies is possible increased absenteeism/LTD, and higher average longevity (more pay, vacay, etc) across the entire pilot group.

There's a possible upside in that they won't have to hire and train replacements quite as often, which is amplified at multi-fleet legacies where one old senior guy leaving triggers a cascade of training events. It's not just the cost of the training, it's also the cost of all those pilots getting paid for many months while not being productive.