HI Brett, we don't plan to get rid of NDI. What are you looking at for CDN ? eCDN is supported for Live Events. With View Only meetings those are distributed using CDN, but the View Only meeting experience does not support eCDN providers at this time. https://docs.microsoft.com/en-us/microsoftteams/view-only-meeting-experience

I'm asking this on behalf of another colleague. Will Microsoft "eventually" be using variable bit rate streaming for Teams live events or will the platform use a "lowest common denominator" bit rate on a longer term basis?

Live Events today uses adaptive bitrate streaming profiles, we don't use a lowest common denominator approach today with out CDN. As noted you can also add an eCDN to help with bandwidth management for corporate locations.