Will all accounts eventually be upgraded to 2023.1 by the end of Q2? Are there ever situations where account upgrades get delayed? I'm asking because I have an app that needs to work differently in 2022.2 than 2023.1, and I'm wondering how long I might need to support 2022.2.

Yes all accounts should be 2023.1 by end of April

I haven't yet had a situations where upgrades have been delayed past end of a Q. Agree with Suitestallion above that everyoneshould be migrated by end 4/23