My prediction:
If AfD is formally banned, it's only a matter of time before another party rises up in its place.
Designating the party as "right-wing extremists" officially, or even banning it will do nothing to quell the dissatisfaction that drives people to support the party. This is the case, no matter what one may or may not personally feel about the AfD platform.
If AfD is taken out as a channel for that dissatisfaction, the dissatisfaction will just find another channel.
Also, it's amusing to me that I'd bet this is the same people who are against legislating against prostitution by instituting the Nordic model, on the basis that "it will just drive prostitution underground". But the possibility that banning right-edge parties might drive that movement underground - with very much unpredictable consequences - doesn't even seem to be considered.
RT: https://hell.twtr.plus/objects/e57c780e-83c5-4673-8019-dbde1e2d47b2