The threat of the AfD is going to be used as a cudgel with which to keep the left in line, even as the CDU (and inevitably the SPD) end up adopting pretty much exactly the AfD's position on immigration thinking that this will win back AfD voters.

That's exactly what we've already seen over the last ten years of the AfD getting ever stronger, and especially the last year or so after the Correctiv exposé on what the AfD says in private. The AfD even bragged that this is what's happening and it's what they want, but nobody paid attention to that part.