Just to be clear, if they did remove his contributions they must also make so none of the left over code is a derivative work. That would be a task beyond even a security audit.
Mojang is not in a very business friendly situation right now. The only 100% not-lawsuit-libel approach is to either open source minecraft or rewrite the entire thing. They are still open to lawsuits related to the existing distributions but the traditional settlement is a combination of stopping to infringe and medium cash payment.
This is why, when folks say "CLA's are not necessary, you'd just remove the code" (like bradley kuhn recently did), i think they are very very wrong :)
Mojang is not in a very business friendly situation right now. The only 100% not-lawsuit-libel approach is to either open source minecraft or rewrite the entire thing. They are still open to lawsuits related to the existing distributions but the traditional settlement is a combination of stopping to infringe and medium cash payment.