I doubt there will ever be a monorail, for basically the same reasons that Disney hasn't expanded theirs. Fixed rail transit systems are really expensive, and the layout of the resort will never be conducive to an effective routing that stops enough places to make it worth the cost.
At first thought, we would say the system should connect the two Citywalk areas (and maybe an ESR stop if it is on the route). However if a Universal hotel guest wants to visit the parks in the other resort area, they would first need to take a bus (or a boat, or walking) to get to the monorail station, and then ride the monorail to the other Citywalk area before they could enter the parks. From a guest prospective, this multiple ride scheme is likely to be considered as less convenient than just taking a direct bus.
You might be able to alter the path and extend it to add stops at a few more hotels in the south resort area, but it will complicated and a significant increase in cost because the hotels are going to be spread in many directions from where the south city walk is likely to be. That still wouldn't really help guests at the current north resorts, and would also make it harder to add stops at the convention center and a possible future I-drive light rail station.