I don't think it is possible that the three religions will join together.
First of all, Judaism is essentially a religion for Jewish people and has appeal mainly for that ethnic group. Though there are sects which allow conversion, it is not very common. The belief in One God and its teachings, however, gives many people a favorable view of the religion.
Christianity is a religion with a wide scope, however the problem I see with the religion is that it is associated with colonialism in many parts of the world. Also, the belief in trinity alienates many people who do not accept it. The appeal of the Christian religion are the teachings of Prophet Jesus (peace be to him).
My belief is that Islam is the religion which has the most potential to unite different people, though many people on this forum would not agree with me. This is evident to me by the fact that wherever Muslim followers exist, Islam has become a part of the region and culture. Only a minority (20%) of Muslims are Arabs. This becomes even lower if we only consider the original Arab tribes of the center of the Peninsula. Muslims accept all the Hebrew prophets such as David, Moses, Jesus, John (Yahya), along with the Prophet Muhammad (peace be to them). Muslims also believe in the fact that all nations of humanity where sent prophets, though we only are informed of the Middle Eastern prophets.
For Muslims, atleast, Islam is the continuation of the Jewish and Christian traditions. This is the reason why it has an immense following among the descendants of the ancient Christians (Egyptians, Levant, Yemen, Turkey) and Jews (Palestine) of the Middle East.
The Prophet Muhammad (peace be to him) is praised in Islam because he is the final prophet and the greatest example to humankind. Also, his message is the one we have most knowledge and detail of.
As related by the Prophet Muhammad (peace be to him), "My similitude in comparison with the other Prophets before me is that of a man who has built a house nicely and beautifully, except for a place of one brick. The people go about it and wonder at its beauty, but say: "Would that this brick be put in its place." So I am that brick, and I am the last of the prophets." (Sahih Bukhari)
Within Islam one hardly has to point out the hatred between Sunnis and Shiites, apparently over some incredible little nuance that happened more than a thousand years ago.
There is a disagreement between Sunni and Shiat, however, this occurred centuries ago and was of political origin. Sunni and Shiat Muslims generally don't define themselves as of a sect, but as Muslims. There are five madhabs (classical schools) of Islamic thought and each differ in minor areas (such as where to place hands while praying). These five schools are defined by their teachers Imam Ahmad bin Hanbal, Imam Shafi'i, Imam Malik, Imam Abu Hanifah, and the Shiat school Imam Jafari. All of the five Imams were acquaintances, and learned from each other.
It is in the interest of those uninformed of Islam to attempt to show that Muslims hate each other, when this is not clearly a case. If anyone is interested and wants to ask more questions, I will be glad to answer.