The encyclical will be signed by Pope Francis on October 3rd at Assisi. The same city where John Paul II met with and prayed with the leaders of a plurality of religions. This is THE encyclical that will force the papal critics into sedevacantism and out of the Church, formally. If it does not use Papal Infallibility, then I think it will be followed by a document that does use PI to assert the same teaching definitively. No doubt that the usual papal critics will accuse Pope Francis of heresy on this one as well.