It is unlikely that any browser will ever require ECH without a fallback to non-encrypted ClientHello.
If the CDNs come under pressure, they can stop allowing ECH, just like they stopped allowing domain fronting. Unlike fronting, they can do this selectively -- like, only if the client is in $COUNTRY and the hostname is one of XYZ.
If the CDNs come under pressure, they can stop allowing ECH, just like they stopped allowing domain fronting. Unlike fronting, they can do this selectively -- like, only if the client is in $COUNTRY and the hostname is one of XYZ.