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.
Is the signing date when the contents will be available to the public?
I’m not sure.