petersonal - to be perfectly clear - both Exchange Server 2016 and 2019 will still be supported after January 9 2024. "Extended support" does not mean "no support". It means "no new features are considered after X date" and "security updates are still supported".
kenmich350 - it won't be too long now that we will have more to say about what comes next, but the time is not here just yet.
jvanbeusekom - In your hypothetical scenario, if we do release the "last" CU for Exchange Server 2019 and let's say that we did introduce a impactful regression, we would absolutely consider releasing a fix for it, of course. Remember, we have 3 types of release vehicles: SU (security updates) CU (cumulative updates which roll up all feature and security updates) and HU (hotfix updates, which can be feature fixes for a specific CU, not security related). So - we have enough levers to pull if we ran into this scenario.