I posted my experience updating to CLEAR NextGen here in the main consolidated CLEAR thread. However since fellow UA Elites were debating the usefulness of CLEAR even getting it free as 1K/GS, the quick bits I learned:

1. The promise of NextGen enrollment includes that there will be fewer ID checks.
2. CLEAR NextGen update includes taking an updated photo for facial recognition, and said image is compared against whatever ID (passport, state ID) you enrolled in CLEAR with. Gives CLEAR the ability to say the person present was compared to a file photo, which was compared to a photo accepted as ID by either a US state or a federal government (goes in line with #1 on convincing feds to do less random ID checks).
3. CLEAR NextGen updated kiosks can support reading the biometric chip from the passport to get a direct copy of that photo, rather than just scanning the bio page and using the physical scan of that photo. However, some kiosks have the update to take the next gen photo of you at the kiosk, but not read the biometric passport chip (in which case they won't be able to use the passport at all for nextgen document update).
4. With some qualifying weasel words and a scant lack of detail, I was told that the NextGen CLEAR experience "should start rolling out in February 2024". What exactly that would entail remains unclear, but given that I cleared Port Canaveral in about a second without presenting my passport solely using my face without glasses at an IDEMIA reader, I imagine the new CLEAR promise is probably similar - either barely stop for just a couple seconds or keep walking for instant ID check.