I don't think that it would take that much.

It is my understanding that the A18 CPU is pretty well understood already. AFAIK it doesn't have the new architecture that is keeping the Asahi team from supporting the M4 and M5 for example.

But I guess we'll have to wait for devs to get their hands on a Neo device

If Asahi runs well on this I'd be very tempted to get one as a dedicated Linux machine

M4 is basically an upgraded version of the A18.

M1 was A14, albeit upscaled.