Hard to really project out that far, but non-Catholic Christians should become a minority around 2040.
interesting that the percentage of non-Catholic Christians has stayed mostly steady for nearly 3 decades. also surprising given immigration that the Catholic percentage has lowered a bit.
religious people generally have higher birthrates, so the way we get to a Chrisitan minority would be a) massive immigration of Muslims, Hindus, Sikhs, Buddhists, etc. and/or b) a dramatic decrease in religiousity in future generations.