You make some interesting points. I wish to take them one by one, as you seem to have thought this through rather intelligently, unlike many of the shrill responses that one gets in a thread like this, both from Believers (of one persuasion or other) and Atheists.
Evidence suggests that religions will rise and religions will fall. Some larger sects will schism, some smaller sects will re-unite. The geographical spread of religions will change and there will continue to be a minority of nonbelievers under differing degrees of persecution around the world. In the tens of thousands of years we've had formal religions, various sects have claimed to have unifying creeds, but none have been successful.
This is an interesting point. Christianity is a case in point. Even within Lutheranism, there are schisms a-plenty, primarily based on two things: (1), Liberal v. Conservative, and (2), ethnicity. Now the ethnic part isn't so much a schism, really. For example, ELS (Evangelical Lutheran Synod) is in Communion and Altar Fellowship with WELS (Wisconsin Evangelical Lutheran Synod). The first is basically a bunch of Norwegians around Minnesota, and the second a bunch of Germans in Wisconsin. They agree with each other in Faith, but originally worshipped in different languages and in different places. Hence, two Churches.
The first issue is much more of a schism. When ELCA (Evangelical Lutheran Church in America) decided in 2009 to ordain partnered homosexual persons and marry them, numerous groups broke away and formed their own groups of Churches, the largest in my area being LCMC (Lutheran Congregations for Missions in Christ). They also took the largest ELCA parish in the city along with them. So I do see your point here.
Personally, I am inclined to think that something resembling a World Scripture will almost certainly be created, probably very skillfully. It will find a way to blend the various stories of Jewish, Christian, Muslim, Hindu, Buddhist, and many other religious narratives in such manner that they flow smoothly. It will also find a way to distill the morality of the Bible, the Qur'an, the Analects of Confucius, and others harmonised and forming a smooth, clear edifice for one to observe.
Unlikely, Jews, Christians, Muslims, etc. can't even agree on a World Scripture of their own faiths. Hinduism isn't even one religion, it's an umbrella faith with thousands of different permutations and religious scripts.
I am not sure I entirely agree with you on this one. Muslims all agree that the Holy Qur'an is Scripture. Now, they may disagree on what constitutes valid Haadith, but that is a bit secondary. Jews all agree that the Hebrew Bible is indeed the Scripture of their Faith. They may vary as to how to interpret it, but there is no disagreement on what it is. Christians do disagree on the contents of the Old Testament, with the Catholics accepting extra books that the Protestants do not, and the Orthodox accepting one or two more, and the Ethiopian Church accepting still more. But they all agree on the New Testament, which, lets be honest, is more central to the Christian message. They may again, differ as to how to preach the message, but the content...
Hinduism does get a bit odd. I won't dispute with you that there are a shit-ton of varying texts of varying degrees of importance to different Hindus. And what exactly is a Hindu? Some people count Jains as Hindus. There are even Buddhists in India who are counted as Hindu.
I think that if a Commission of Ecumenical Translators ever DID meet with the intentions of creating a world Scripture such as the Orange Catholic Bible, it would have to choose wisely from all the Scriptures that are validated by people everywhere. It would not be able to restrict itself to those that only the majority, whatever the Hell that is, use. I mean, Hinduism is the world's 3rd largest religion. Even though they as a group do not all accept the same texts, there are some that are common, more or less, to them as a group. I do think it could be done. As to whether it will be, well, that is another matter.