Im of the opinion that it’ll be rapid. Apple spent last year mapping major cities with cars equipped with 360° cameras. They did Toronto back in May of 2019.I doubt it will be rapid...maybe a little quicker.
Boston, Philly, Chicago, Seattle would be my next guesses....or actually, Dallas first.
I think the plan for hitting major cities first and then expanding out makes sense (and yes, should be much quicker with residential areas).
When they talked about the new maps, they said processing happens quickly after the hard drives are transferred from the car to Apple Maps’ team. They have all the data and photographs already.
So, my guess is that they’re just testing Look Around with the few cities they released and once they’re happy with how it works, they’ll turn on the the cities they have the data for.