What do we reckon? Nothing to indicate in the specs (unless I've missed something). My Cameras use UHS-ii SD Cards and transfer rate with a UHS-ii USB-C dongle on a 2019 MBpro is nice and speedy. I'd love to ditch the dongle (seeing as that's the idea with the ports) but I have a sneaky suspicion the slot will not be UHS-ii. Apple would probably love to limit the speed and therefore reduce the chances of people expanding their macbook's storage with a reasonably quick Micro-SD card in a caddy that sits flush in the new body.