I cannot contain how much possibility an omni-coaster has. There are so many possible ways you can use it, from a dark ride with (a lot) more umph (cosmic rewind), to making an already intense coaster even more thrilling (Hollywood drift) to a crazy mix of both thrill and immersion. unfortunately, I have only ridden one omni-coaster and watched a POV of another, but from what I have experienced it drastically enhance the experience. From the first turn in the cosmic rewind I was absolutely hooked, and that Hollywood drift looks to be a serious contender for best coaster in the world, or at least the states. I am confident that Omni coasters will become the new standard for coasters, and I can't even imagine the possible directions Universal or Disney(if there still in the picture) could take this mechanic. Now, if Universal slaps a Kuka arm on to a coaster... now that would be something else entirely...
I don't remember the omni coaster being that taxing when it comes to down times, and there are much, MUCH more complex rides that still handle great, or at least good enough for most people.
Yes, omnicoasters have a lot of promise, but also add layers of complexity that can create a lot of issues. I subscribe to the KISS (keep it simple stupid) method, and layering in more degrees of motion which then leads to more forces to control from various directions, and you have a recipe for an attraction the spends more time SBNO than entertaining guests. There's a reason X2 is the only coaster of its kind in North America and why parks are jumping to install something like Mission Ferrari anywhere else in the world.
It's great to dream and envision the future of ride systems, but I don't see any trend emerging to suggest that parks will start rushing to install omnicoasters around the world, like there has been with other coaster and dark ride types.