Pope Francis, who is staunchly anti gay marriage, has indicated he intends to cannonize Pope John Paul II by the end of this year due to the fact that Pope John Paul's second miracle has been verified.
Pope Francis has also indicated he is re-opening the case for sainthood for John Paul's predecessor, Pope John XXIII.
And Pope Francis is also championing the case for beatification of Pope Paul VI.
Due to Vatican influence, I really can't see gay marriage happening in Italy any time soon -- or ever for that matter -- in a place where Popes and Saints reign supreme. In fact, unlike other prominent people in history, I have never heard of any Pope or Saint being gay.
Noel I. Garde, in his gossipy 1964 book Jonathan to Gide: The Homosexual In History, included John XII (r. 955-964), Benedict IX (r. 1033-1045; 1047-1048), John XXII (r. 1316-34), Paul II (r. 1464-1471), Sixtus IV (r. 1471-1484), Alexander VI (r. 1492-1503), Julius II (r. 1503-1513) and Leo X (r. 1513-1521), along with Julius III, in his list of “gay popes.”
I don't see the designation of "saint" to John Paul II having any nexus to the prospect of allowing same sex couples to be married in Italy. I do concede the homophobic Catholic Church does have a strong sway ... and I would say too strong of a sway in Italy. I can see the prospect of Civil Unions for same sex couples in Italy similar to as was had in France until they joined the group of more progressive and enlightened nations.
As of today, Pope Francis has positively cleared the way for both Pope John Paul II and Pope John XXIII to be canonized before the end of the year. The word in Italy is that the ceremony will take place on December 8, which is the Feast of the Immaculate Conception and the start of the Christmas Season in Italy and a major holiday with all government and private offices, schools, businesses, etc., closed. This will be a great day for Italy, Italian culture and the Italian people.