Some people will always believe anything they are told... I give you low-IQ Trump voters!

Christianity might die down at some point but there will always be some sort of religion. There are people who are weak and want someone else in control or to blame things on. "Alas, it was god's will!" Or, "It was the devil's work!"

I call bullshit on all of it!

I don’t really care one way or the other.

Well, there will always be 'religion' around. Some people have a need to know the "meaning of life" and religion is something that resonates with them. I don't give a toss about it, but do give a toss that those so called religious people have a need to "force" their beliefs on others.

A. I think a religion's "health" is all related to birth rates and how much forced indoctrination there is. I don't see it surging, but I don't think, at least in the US, people will ever be forced to meet in secret.

B & C. Probably as long as humans have left. I see a catastrophic event that ends [human/most] life on Earth to be way more likely that the complete abandonment of all religion. Hell, humans are starting new religions still.

How many years ? I think it is really up to us. As in any journey a road map to rid ourselves of religion would be extremely useful . It would also be extremely complicated but not unfathomable if we have Plans A to Zee and beyond. We could start those plans now[ and below are some suggestions], plenty of these will be wrong but they are countless if we are determined.

1. Learn how to dialogue with religion in a fashion that does not upset them . There are thousands of Interfaith organizations which discuss common problems between churches. We could organize a way into these on the basis of free speech. These discussions would rely largely upon logic,reason and science.
2. We should merge as many non religious organizations together as possible. A world wide organization would replace all the existing ones.

Difficult ... YES but we have to begin somewhere !. I will stop suggestions there but I am sure more would follow once the ball is rolling. Have faith in Humanity !

When a "religion" is backed by blood and violence with the theme of "join or die" as long as that organization is allowed to exist by society at large it will continue ti thrive. You have to remember that it has been LESS than 2,000 years and for much of that time was the sole form of government. Right now we are seeing its last stages of decay when it still is powerful but dying none the less...

Even if religion goes away, the ruling class will always have other things to divide the lower classes on, such as race, nationalism, guns, etc. They only need a few issues to make that work as long as critical thinking is rare and the mass media is controlled by and supportive of the ruling class. If the gullible and weak don't have religion around to tell them what to think and what to do, they will gladly take on whatever a demagouge or the mass media tell them to believe or do. Few people have the strength and guts to think for themselves.

a) No Christianities days are numbered.

b) Christianity is already dead, like define it, if you can.
With over 32,000 Christian denominations it's a certainty that Christians don't know what Christianity is.

c) To become religion free will take political will because religion is just a political tool and nothing more. While the faith has dried up and blown away ages ago, the power structure is still tempting to ambitious little men. The entirety of the Republican party is exclusively based on American Conservative Christianity which adequately explains their overwhelming stupidity in Science, Logic, Debate, etc. After all they were in charge for a couple of millennia and literally nothing at all got done.

A) Depends on if there was another "revival" like the one in the mid-19th century.
B) In many countries it is on the way out, not so much in the US.
C) Who knows?

One other thing that you have perhaps to think about is. Has Christianity really survived the last two thousand years, or has it reinvented itself so much, several times over, that it is not really the same thing at all. The name is the same, because reusing the old name helps you carry the old prestige forward, but would a Nazarean have understood the religion of Rome after St Paul, or a follower of Paul recognized that of Constantine, certainly the post imperial church of Rome was completely alien to the Greek church, the reformed protestant church of Luther was a different thing again, and so on, though Baptists, Methodists etc.

Maybe it is coming to the end of the line now. Yet there are already 'green' 'Christian' environmental movements, in a church which was supposed only a short while ago to be praying for the destruction of the world. The great trick is to use God and the Christian/Jesus name, in whatever form you like to add authority and prestige to whatever view you want to pedal. But maybe you can only get god to change its mind so many times before people start to see through the trick, and the prestige they thought they carried forward starts to wear thin. Then its done.

Speculation. As a lifelong atheist, I don't care about Christianity, except when Christians want to stop women's control over our own bodies.

A bumper sticker on my car:

Keep your theology
Off my biology.

Forty years ago, I had a National Abortion Rights League button:

Keep your rosaries
Off my ovaries.

I give christianity another 50 years before it is on the edge. As it is right now a couple percent on it's number leave every year. This only leaves the nut jobs. Sadly other religions are on the rise.

A. Hope not.
B. Who the fuck knows?
C. If even in a non believer forum place like this we're still obsessing about bullshit, then it will take more years than necessary.

As long as there is money in politics, there will be Christianity and it's "relatives". The "faithful" will always seek a "higher" power to make them feel good about their choices, and cope with the inevitable.

It’s not as much the flavor ..as the effect…

Religion is definitely on it’s way out. Watch the educated nations, and as with all other advancements (good or bad), the less developed (or educated) will eventually follow. Our interconnectedness (Internet) and use of ‘smart phones’ is speeding the process!

No need for guesstimating years, the trend is here, humans, culturally evolving ~

Catholisism`has effectively been a world power , quilting the poor into donating to the rich for centuries . i'm quite certain they will continue to come up with ways to maintain that status quo . And while many religions have fallen by the way side , other equily insane concepts arise to replace the ones that die out . There will always be the the insane and the quilable , as long as there are charlatins around to cheat them out of their money .