As stupid as that sounds, you are not totally wrong.

@[email protected] and @[email protected] you are misunderstanding what "observable universe" means. The observable universe is defined by the particle horizon, but the universe that can affect us in the future is defined by the event horizon. https://en.wikipedia.org/wiki/Cosmological_horizon says

The particle horizon differs from the cosmic event horizon, in that the particle horizon represents the largest comoving distance from which light could have reached the observer by a specific time, while the cosmic event horizon is the largest comoving distance from which light emitted now can ever reach the observer in the future.

But even the cosmological event horizon distance is dependent on our model of the universe's expansion, which in turn depends on the content of the universe. An event such as a vacuum collapse will drastically alter the content and the expansion rate, rendering our calculation of the event horizon invalid. So "snap changes..." may in fact be the case.