This solution is incredibly stupid. This will kill the entire forum ecosystem 
Mixer signature campaigns aren't the only signature campaigns around. There are other more. Are you saying that removing mixer signatures will kill the ecosystem of the forum? Don't overreact. 
There are already some users here who are applying for other campaigns that aren't a mixer. I don't know the reason though because they can still wear it until the 31st. Maybe they're afraid that by next year, there will be no more open spots thus, they are applying as early as now. I will not be surprised if, by next year, more campaigns that aren't a mixer will emerge, but for now, they can still advertise it until the end of the year.
On the other hand, there will be some that will milk them until they (mixer owners) themselves will just stop their campaigns.