Democratic nominee for vice president Sen. Tim Kaine (D-VA) is often described by news media as a "devout Catholic" so he is making news when he predicts that the Roman Catholic Church will eventually change its position on what is called "gay marriage."
For a lay Catholic, Kaine is presumptuous in the extreme but there is a also larger problem with the way secular news media cover the immutable doctrines of the Catholic Church. The secular press assumes that a goal of the Church should be to "get up to date" in order to make itself "relevant" to current social trends. That is NOT the purpose of the Church. The purpose of the Church is to remain true to eternal teaching of the Church and not to adapt to passing fads. That is why doctrinal change happens only very slowly in The Catholic Church over centuries and not mere decades.