Orthodox quantum mechanics intrinsically requires an observer - since the only connection from the mathematical formalism to physical reality is through the measurement axiom (probability of observing something given via Born rule, etc.). Otherwise, no assumptions about physical reality are made, and QM enables (maybe even encourages -- e.g. Bell's theorem) one to take a non-realist position, namely that there exists no independent (of observation) reality out there.
Given such a position though, what meaning do claims about the distance future such as "The universe will end in a heat death" have? By their very premise, there can be no possible observers left at that time - but then, who is doing the measuring? Or, put differently, if there is no possible way to observe a prediction, then according to a non-realist view such a prediction should be meaningless.
Are we then to assume that all such predictions about the distant future when there will be no observers left, are made in a realist context? But even then, strictly speaking, if there is no one left to verify the prediction, it is untestable - and so in some sense epistemologically meaningless (and is in the same equivalence class as claiming, say, that "the Earth is supported by a giant invisible turtle").