Thread upgrade for Zigbee devices

Apologies if this has already been asked.
My understanding is that Zigbee devices are theoretically capable of being upgraded to support Thread integration but this depends on the chip and available resources.
Can someone answer whether any of the existing Sonoff Zigbee devices are capable of the upgrade and whether this is the development plan?
Thanks
Steve

Is anyone able to help me with this question?
I am needing to purchase some more devices and don’t want to continue with Zigbee if the new matter devices support Thread rather than just direct wifi
Thanks
Steve