You asked: I have learned from the reading of The Urantia Book that there were 2 previous rebellions before Lucifer’s. Since there have been a total of 3 rebellions will God allow for a fourth or more?

Thanks for this most interesting question. I found two passages that address this issue:

45:2.1 The chief executive of a local system of inhabited worlds is a primary Lanonandek Son, the System Sovereign. In our local universe these sovereigns are intrusted with large executive responsibilities, unusual personal prerogatives. Not all universes, even in Orvonton, are so organized as to permit the System Sovereigns to exercise such unusually wide powers of personal discretion in the direction of system affairs. But in all the history of Nebadon these untrammeled executives have exhibited disloyalty only three times. The Lucifer rebellion in the system of Satania was the last and the most widespread of all.

And this one addresses the problems associated with the fact of distance from God as a factor in rebellion:

50:1.3 Being quite alone as representatives of divinity on the individual planets, these Sons are tested severely, and Nebadon has suffered the misfortune of several rebellions. In the creation of the System Sovereigns and the Planetary Princes there occurs the personalization of a concept that has been getting farther and farther away from the Universal Father and the Eternal Son, and there is an increasing danger of losing the sense of proportion as to one’s self-importance and a greater likelihood of failure to keep a proper grasp of the values and relationships of the numerous orders of divine beings and their gradations of authority. That the Father is not personally present in the local universe also imposes a certain test of faith and loyalty on all these Sons.

Freewill choice is given by God to all of the personalities in all of the evolutionary universes. That being true, there will always be the potential for evil because God does not interfere with free will choice. In Caligastia’s case, he freely chose to join Lucifer’s rebellion; the consequences of that rebellion involved the quarantine of our entire system from the celestial circuits and we see its repercussions still working themselves out in our world.

But since we now enjoy the ministry of Christ Michael himself as our Planetary Prince and system Sovereign, it is probably not possible that there will ever be another rebellion here, in my opinion.

These events are pretty rare in any event; it could be that in ages to come there may be potential for other rebellions with other new systems and other planetary visitations, but it seems to me that we will not have to go through another one. I think that we can rest easy, knowing that Christ Michael of Nebadon is now at the helm.

134:8.9 On an afternoon in late summer, amid the trees and in the silence of nature, Michael of Nebadon won the unquestioned sovereignty of his universe. On that day he completed the task set for Creator Sons to live to the full the incarnated life in the likeness of mortal flesh on the evolutionary worlds of time and space. The universe announcement of this momentous achievement was not made until the day of his baptism, months afterward, but it all really took place that day on the mountain. And when Jesus came down from his sojourn on Mount Hermon, the Lucifer rebellion in Satania and the Caligastia secession on Urantia were virtually settled. Jesus had paid the last price required of him to attain the sovereignty of his universe, which in itself regulates the status of all rebels and determines that all such future upheavals (if they ever occur) may be dealt with summarily and effectively

Thanks again for this interesting question!