Or of course "unavoidable"; either will do equally well.

Although "horizon" is a nice term, I don't think "this horizon" will work here in English, even though you can talk about things being on the horizon, meaning anticipated in the foreseeable future. It's simply that "horizonte" is used in Spanish more than "horizon" is used in English in this metaphorical sense.

But "prospect", in the sense of an anticipated future scenario, is really quite close to "horizon", I think, and to me it fits well here. The idea is a bit reminiscent of Sartre's famous comment that man is "condemned to be free", though here it is suggested that we are condemned to be at the mercy of contingency. Our future is uncertain and there's nothing we can do about it.

The point is that "horizonte" doesn't mean a particular outcome or fate or destiny; it's not that our fate is inescapable. That would imply that it is predestined, which it not at all what is being claimed here. This is saying that the situation of being subject to contingency is inescapable.