The fleet preview is out. No mention of the Mach 1 though :frown: No exterior updates for 2021 by the looks of it. The order guide came out within days of the fleet preview last year, so it should drop soon...
I don't know if this is any good to you, but the 2020 Fleet Preview has some details about the 2020 Mustang in it.
https://www.fleet.ford.com/resources/ford/general/pdf/brochures/2019/2020_Fleet Preview Guide_Spreads.pdf
Something to peruse while you wait for the order guide.. like myself :)