Either a Heat Death where the universe has no thermodynamic free energy left and it entropies, or the Big Rip, where galaxies, atoms, and possibly spacetime itself are torn apart. According to most hypothetical models. I'd say we'd have to wait and see? But that's going to happen a long time from now and we won't be around anyway. I hope.
We'll grab a venti. Unfortunately, they don't sell it in buckets. I could use a bucket.