Resolves YES for all players included in the 26-man (or whatever the final number) squad reported to FIFA at the final deadline (to be established at a later date).
Subsequent changes to the squad don't count, i. e. players who are out for injuries or other reasons after the deadline still resolve as YES and their replacements resolve as NO.
Thanks to @ADings for making the German Euros Roster market, which encouraged me to pull the trigger on this and for nailing down a reasonable resolution criteria, which I have largely borrowed from for this market.
Please add your best guesses and anyone you think might have a slim chance. A lot can happen leading up to 2026!
I've added all players who were brought into the Nations League that weren't already included:
Marlon Fossey (Standard Liège)
Auston Trusty (Celtic)
Tanner Tessmann (Olympique Lyon)
Patrick Agyemang (Charlotte FC)
Brian White (Vancouver Whitecaps FC)
Patrick Schulte (Columbus Crew)