Religions end for a number of reasons, but spirituality will persist so long as the children of God exist on Earth.
I learned recently of something called "second death" and instantly knew what it was.
You see, each of us is a spiritual being wrapped in Homo sapiens flesh. Being outside of the body and moving about with the ability to see clearly without human eyes is quite a trip. So long as such things are possible, religions will persist -- not individually, but as a social force.
The first death was in the Garden -- a non-physical place of spirit. This is when we took the "forbidden fruit" of selfishness -- separateness from God. This is the first death -- separateness from our true selves, falling into the false self of ego.
(And Slarty, what you said before about trying to get rid of ego has stayed with me, nagging at me. And now I know. Yes, you will lose yourself if you attempt to get rid of ego without accepting your spirituality. That's akin to second death.)
When the rescue mission packs it in and leaves (see Genesis 6:3), those who don't choose to return will be abandoned and let slide into second death -- the second separation. I guessing it's a separation from the false, ego self, into oblivion. The being might end up like the main character in the animated film, "Waking Life" -- a perpetual lucid dream that goes nowhere. But as with any dream, even lucid ones, they can turn into nightmares, like a lake of fire or something worse.
So, individual religions will cease because of wars, attrition, cultural absorption or a number of other mortal methods. But religion as a force will persist so long as spirit persists. Once second death occurs, spirit will be two layers of unconsciousness down and incapable of climbing out of that well.