@BlakeRichardson, going by the WWDC 20 video "What's new in managing Apple Devices", yes, MDM Restrictions Payload will be able to disable this.
"Beginning in iOS 14, whenever a device associates with a Wi-Fi network, it will use a random MAC address instead of the device's true hardware MAC address. For enterprise networks that use captive portals or filtering, the new feature may cause an unexpected behavior as the device may not be identified when it joins. If the device fails to join the network, it will fall back to using its real MAC address. While users can disable this feature in Settings, we've also made it possible to disable it using the Wi-Fi payload."
Whilst I have no news when Meraki SM will support this new payload, I suspect it will be included once iOS 14 is released publically (not beta). Here's a full list of what's coming in iOS 14 MDM: