Ah, another “When is everybody else going to wise up and see things as I do?” thread.
But then will the human race have any use for “Christianity” as a religion? 
Is there any irony in the OP’s wish that by “54000 AD” Christianity will have been rejected?
In my own system of GD scorekeeping:
Points gained for comparing belief in God or Jesus with belief in Santa Claus or the Tooth Fairy: negative 5
Paints gained for mis-spelling it “Santa Clause” negative 15
How many modern religions - by which I mean organized, multi-national systems of faith - have disappeared over the past 2000 years? I can’t think of one.
Certainly if our civilization continues eventually Christianity will fall on history’s trash heap, just like Mithrasites, Norse God worshipers, and neolithic fat chick fetishism.
Christianity is just as stupid as the worship of Zeus, so there is no reason to assume that someday it will be gone and supplanted by something equally stupid.
Although I am sure that as wealth and education spread religion will diminish. But I doubt it will ever be completely gone.
The Greek and Roman faiths, the Aztec religion, and the Mayan religion would probably count.
Let’s not go assuming that history is progressive. Five hundred years from now who knows what Australian politics is going to look like?
Mithraism.
It depends on just how endemic religion really is to the human psyche. In an age of unprecedented scientific understanding, it’s becoming harder and harder to support ancient superstitions as having any rational function anymore, but religion is not rational and a lot of humans seem to invest a lot emotionally in it.
I think Christianity (and religion in general) is likely to fade more and more over coming centuries (I don’t think it will take millennia anymore. The 20th Century was arguably the most transformative in human history). In much of Europe, it’s already becoming something of a quaint institution. It could possibly evolve into something else, or fuse with other religions into some more functional, ecumenical hybrid. If technology and science ever decline, I would imagine humans would return to superstition, but it will probably be new superstitions, not old ones.
It’s denomination-specific. Basically, denominations that have been successful at missionary work in Asia and Africa (most of which are Protestant) are growing quite successfully. The same denominations may also grow in Catholic or Orthodox areas —in fact, the Pentecostals (annoyingly) send out missionaries to convert Orthodox. At least, one church I’ve been to does.
I think it’s worth pointing out that every single Old World religion you two mention has followers nowadays, albeit not very many. (Egypt -> Kemetism, Romans -> Roman Polytheistic Reconstructionism, Greeks -> Hellenic Polytheistic Reconstructionism), and I think the Aztec and Mayan religions may have some local adherents, as well as some neopagans. Either way, it’s worth pointing out that four of those five were wiped out, partially peacefully and partially by force, by Christianity —they didn’t merely fade away into nothing. I don’t know about the Egyptian gods.
(PS. Yes, I stole the Roman and Greek neopagan religions’ names from Wikipedia. Couldn’t remember what they were properly called.)
Those were all national religions - bound to a specific place and tongue. Once you conquered and converted the region, the religion could be eradicated. One a religion starts hopping borders and cultures, like Christianity, Islam, Buddhism or Hinduism did, they’re almost impossible to stomp out. You kill them in one country, they flourish in another.
(Note that according to my own definitions, I do not consider Judaism a modern religion).
Christianity will be rejected when Jesus Christ comes again and puts a end to all rule and authority including religions and established His Father’s Kingdom on earth. When that will be - according to scripture the angels in heaven nor the Son knows, only the Father.
Christianity being a bunch of sets of man made rules, regulations and religious authorities that get in the way of a person knowing Jesus personally.
Is there any irony in denying the truth of Thor on Thursday or the Roman gods on Saturday?
The last one is still going strong.
A brief resurgence in America’s trailer parks. Eventually they’ll invent a fat-loss pill and it will disappear for good.
Fair enough, although they did represent the powerhouse faiths at the time and place. In order for Christianity to fall quickly you’d have to overthrow Western society, which is, I’ll admit a lot less likely than in times past.
But erosion due to education and prosperity is happening around the world.
What about Syrian-Egyptian Gnosticism, Adoptionism, Psilanthropism, Manichaeism, or Zurvanism?
It kind of makes no sense to ask “what modern religions have disappeared,” since if a religion has disappeared, it can’t be modern.
The whole criterion of an “international religion” is kind of specious too, since the whole idea of an international, evangelical religion is pretty modern. In classical times, people just used to recognize that local gods varied, and didn’t concern themselves with trying to evangelize them (they still also recognized that they were often consonant with their own gods too, though).
Having said that, Mithraism was an international religion which disappeared. You could also add movenments like Gnosticism.
Historically, local religions have not faded away organically, but been supplanted by force. Christianity and Islam being the most notable supplanters. It is true that neither of these religions is likely to be supplanted by force, but that doesn’t mean they’ll hang around forever in a post-magical world.
The important thing is when will the rest of y’all convert to Athenism.
32nd of Never. Got it.
When people stop making threads about this.
What are the odds of getting a handy from her avatar?
IK’m going to assume that handy = handjob and release the bees.
It’s not personal, just policy.