I haven't heard anything on that. It's really such an odd omission to not support USB-C Alt mode. It renders the Pixel devices incompatible with AR glasses.
Yea that was probably the only reason I would have upgraded from my 7 pro, and if it's not there, looks like the 8 series is a pass from me.
The fact that there is no mention of it anywhere when even the latest iPhones mentioned it seems like enough evidence, but I even contacted Google pixel support and they said the same thing, doesn't have it.
Update: There's actually a tweet up on !googlepixel@lemdro.id suggesting the hardware supports it but it's disabled in software. Should be able to enable if rooted.