Wouldn't it be mostly a software issue to make the MFC-101 compatible with the Axe-Fx 3? Then all you need is an adapter for the FASLink 2 port, right?
Sure. But it’s a pretty significant change for the MFC, going from just X/Y to Channels. Can the MFC’s hardware even handle that? Who knows. And frankly, it doesn’t get much love from Fractal. Will they dedicate the needed resources? They have a lot to do I would guess.
Then we don’t know whether the new Axe even sends the needed SysEx messages out for bidirectional communication via MIDI. Here I’m a bit more optimistic because I think some artists use third party controllers with Axe FX.