Our default assumption is that the universe still has billions and trillions of years left to evolve. But if the antropic principle is true in a strong sense, then the existence of the universe is not guaranteed anytime after the present. For example, our ecology will probably perish in the next few hundred million years due to solar evolution. The sun only “had” to keep earth in its habitable zone long enough to evolve us.
Dark energy became the dominat force seven billion years ago — halfway into its existence. Future evolutionary scenarios besides the Big Chill are possible. This may result in a big rip, big snap, or death bubbles — various scenarios that result in the end of spacetime.