To be precise, the cosmic event horizon isn't shrinking: it will always remain at the Hubble Distance. However, everything that isn't gravitationally bound to u

To be precise, the cosmic event horizon isn't shrinking: it will always remain at the Hubble Distance. However, everything that isn't gravitationally bound to us is receding from us at gradually increasing speed. The cosmic event horizon is the distance when that speed exceeds the speed of light, making it impossible for light to reach us. Just like an object entering a black hole, it will take forever for objects to actually cross the horizon, but they will smear out and redshift, becoming too faint to see, in some finite time.