No, there is another option, as Eve has done.
Wi-Fi, Bluetooth, and Zigbee all operate in the same physical radio spectrum. So a radio which has been used for one can often be converted to one of the others. But it can’t do both at the same time, because it would miss some incoming messages.
Eve chose to convert many existing Bluetooth devices over to thread. This could be done with a firmware update. (A few could not be updated this week, and have to be replaced with new models.)
That’s fine for something like a motion sensor. But if you did it for a hub, you would lose zigbee In order to gain thread, and most systems don’t want to do that.
In the case of the V3 models, they were designed as “Thread capable“ and have a radio inside which can be used for thread while a different radio is still used for zigbee.
Homekit has already enabled Thread in the Mini HomePod hub, So they can already handle Thread devices.
Some Amazon echo devices will also be able to handle thread.
It seems likely that Aeotec will update the smartthings V3 hub for thread, but it has not yet been promised.
Wi-Fi devices will almost all continue to use Wi-Fi, not thread, because the two protocols really have different purposes. You can’t send audio or video over thread or zigbee or Z wave effectively: the message sizes are too small. And, of course, Wi-Fi can operate without a hub, which some people prefer. But thread and zigbee can handle more devices per network and are way more energy efficient, which allows for battery operated devices that don’t have to be recharged every few days. So both have a place.
The expectation for matter is that Wi-Fi and thread will be the most popular protocols to begin with, although zigbee may also be included.