As much as I don't deny despising Islam, I have to admit they are NOT the only ones doing dirty work. The Buddhists are playing some filthy games in Myanmar (Burma) against the Muslim Rohingya People. Christians in the Central African Republic are forcing Muslims to become Christian under penalty of torture and death. In India, Hinduism does have an element of nationalistic fervor that can get rather nasty under certain circumstances, against the Muslim minority.
Oh, I'm sure all religions are doing (or have done) terrible things. The distinction I was drawing is that most religions are
capable of peaceful coexistence, even if they don't always do that. Religions which assert rules that apply to non-believers do not have that capacity, as their followers will always try to control those of other religions.
You might have a valid point here. I am not exactly sure what sort of things would have to occur before mankind was ready for a religiously unified world. Possibly religious exhaustion? Exhaustion with endless Holy War/Jihad? I am not sure.
I don't think any possible change could prepare mankind for that, short of a drastic reduction in population (to a few thousand at most). Expecting billions of people to all accept the same holy text, let alone the same religion, simply isn't realistic. Furthermore, it is antithetical to freedom of religion; new denominations (and occasionally religions, like Mormonism and Scientology) crop up all the time even today. To have one true global religion, you would need to ban that from happening.
That says nothing of cultural differences which will influence the religious moral codes deemed acceptable by different groups of people. To homogenise world religion, you must first homogenise world culture. There have been many attempts to achieve that on some scale over the years -- the Roman Empire, British colonialism, and the Nazi regime, to name a few -- and all have failed. Quite apart from it being an immoral cause in the first place, people simply fight back when you try to take their culture away.
A much more realistic goal is to have different religions coexisting peacefully, with mutual respect. At least that has been accomplished in some countries already.