This is simply false. You can accept GPL contributions and clearly indicate the names of the contributors as required by MIT. There is no "incompatible fork".
No, GPL and MIT have significantly different compliance requirements. You cannot suddenly begin shipping code with stricter compliance requirements to downstream users without potentially exposing them to legal liability.
No, GPL and MIT have significantly different compliance requirements. You cannot suddenly begin shipping code with stricter compliance requirements to downstream users without potentially exposing them to legal liability.