Many users on support are asking us what about AX support when we will support it, what card they can use, and so on. I think I might be able to share some secret news. 
We bought a large amount of this card from AsiaRF. It is mentioned in our new FAQ page. 
- There is a planned upgrade pack as we did it in the past for Turris 1.x routers.
More details will be revealed soon.