The frontier I was talking about is impassable. It's "infinitely in the future", aka "never". That's a whole different level of frontier, imho.

Granted, there is a bit of tree falling[1] conundrum here, but that does not make the question less interesting (arguably, it even makes it all the more so).

1. https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest