AFAIK none of the current Meraki AP's contain a Thread radio.
Thread as a protocol is designed for mesh IoT networks.
While it's possible that a thread radio might get put into Meraki AP's, it's unlikely the functionality will open up until there are some enterprise use cases around it.
For example, many Meraki AP's contain both Bluetooth and Zigbee radio and whilst there is some IOT functionality available, it's not super accessible and is more designed for specific use cases such as Electronic Shelf Labels.
So the likely answer is not in the near future.