Where do you think ion propulsion and future engine technology will take us? What are the dangers? Are there other applications?
It will take us further out in space! But where it will also take us is not places far out in space. But also to more local spaces. Solving problems related to it, will give us new technology. And we have no idea where that will take us, in the same way that we did not know how the general theory of relativity and quantum mechanics would bring us GPS-navigation.
The dangers? Hard to say. I would claim that we should be mindful of not using all our reserves of Xenon for this. Other than that. Probably none. Unless it turns out that ion propulsion damages subspace in some way.
Finally. All four pips: