Metal, to reach its full strength, must be worked and heat treated. Carbon fibers must be laid very close together and well trapped in their resin. (You could argue a carbon fiber winder is a "3D printer" but not in the sense most people are thinking.) So anything that takes a big stress, like lightweight frames or cranksets or rims or spokes, are probably out.

But it's going to be used for a lot of other parts.

I'm sort of fascinated by the guy who built the house-sized 3D printer that pours concrete