Yes I agree with Hiram there. The key problem is the word "universe" which I take to mean, in the older conventional sense - "Everything that exists."
In Epicurean theory it is not "Everything that exists" that will collapse upon itself, but only a localized solar system / star system / galaxy or whatever wider astronomical term floats your boat as long as that term reflects something less than the whole. This is part of the issue that "everything that comes together eventually splits apart" but that can't contradict the "nothing comes from nothing" first premise.
The universe as a whole would not collapse into nothing because it is eternal and time (never came from nothing) as well as boundless and there is no space "outside it" or "beyond it" from which it could collapse.
Now of course I know there are modern theories that might contradict this, but we're first concerned about understanding what Epicurus taught. I personally agree with the Epicurean model of the universe, but of course I can still acknowledge that others might want to dispute that. What's important is to stay precise and keep distinction between (1) what we think, what (2) Epicurus taught, and (3) what some segment of modern theoretical physicists might allege.