I'm probably going to sound like a bigoted Catholic here, but I used to be Protestant. When I was still Presbyterian, I had an outstanding pastor. Now we'd sometimes have various discussions, and at least one of them was about revival. We were always singing and praying for revival, but we didn't really do much about it. In any case I don't think we'd though through the ramifications if we did have a revival.
He said to me that he thought that if there was going to be a revival (in Australia at least, since we were talking in an Australian context), it would start with the Catholic Church. In his opinion the Protestant Churches were far too divided, and the Orthodox are pretty much a minority Christian group in Australia (2016 census - 2.7% of population, Catholic 22.6, Anglican 13.3, Uniting 3.7 with other Protestant denominations anywhere from 2.3% to 0.2%). The Reformed Churches (eg. Presbyterian which was my original church) for example were 2.3%.
Now historically major revivals (and I'm talking about major revivals) have indicated one of three things - the approaching end of a civilisation (eg. Roman Empire), national renewal (eg. Wesley in England), or preparation for intense suffering (eg. Welsh revival 1912, two years before World War II). It could even include all three. The point is that while we might be seeking revival, we may not like the circumstances that are going to accompany or follow it.
And it usually starts somewhere innocuous. World War I was at its height and the attention of the entire world was on the Western Front, with millions of young men slaughtering each other like lemmings going over a cliff. The announcements of the Big Four and the Kaiser were the really important bumpf of the day.
Meanwhile God sent Mary to three almost illiterate children in a backwoods village in a lesser European power, Portugal, to deliver a warning, making the sun seem to dance, instantly vaporising tons of water to the tune of the energy requirement of a ten megaton bomb, and protecting all 70,000 witnesses from a single case of eye damage from staring at the sun for ten minutes straight.
He works through the innocuous, hiding if from the wise and powerful and giving it to children.
If a revival starts, it will be on the same basis - right where nobody expects it to start.
So taking an Australian context, I suspect it would start in an ordinary suburban Catholic Church, location determined entirely by God. There would need to be the threat of intense trouble on the horizon, so that we're shaken out of our apathy and faith in this world These pending disasters could be of a religious or national nature or both (eg. perscecution of the church, a threat from a foreign power, financial woes), and possibly it would lead to national renewal.
Reading my crystal ball, we're finding the new fascists in some state parliaments in Australia won't even allow doctors the right to their own conscience on whether they can refer a woman for an abortion or not. Religious persecution won't be far behind. In that respect they're on a par with the Nazis.
On the nearby international scene, we live cheek by jowl with the world's largest Moslem nation, and fundamentalism is on the rise. China is making waves in the South East Asian area, which again we border. We have 24 million people to Indonesia's 262 million, China's 1.4 billion (nuclear armed), India's 1.3 billion (nuclear armed), Parkistan's 207 million (nuclear armed), Bangladesh's 159 million, Japan's 126 million, Philippines 103 million, Korea 73 million combined (North Korea nuclear armed).
India and Pakistan have about 110 to 120 nuclear weapons each, and the Korean Peninsula area walks a tightrope of nuclear tinged tension. Ninety percent of our oil supplies come from the Middle East, and that's always a cauldron on the verge of tipping over.
So I'd say if there's going to be a revival in Australia, it will be start in an ordinary suburban Catholic church, where nobody will expect it to happen, and at about the same time, a lot of trouble will hit.
I'd give it about two to three years.