  If dark energy is a form of quintessence driven by a scalar field $\phi$
evolving down a monotonically decreasing potential $V(\phi)$ that passes
sufficiently below zero, the universe is destined to undergo a series of smooth
transitions. The currently observed accelerated expansion will cease; soon
thereafter, expansion will come to end altogether; and the universe will pass
into a phase of slow contraction. In this paper, we consider how short the
remaining period of expansion can be given current observational constraints on
dark energy. We also discuss how this scenario fits naturally with cyclic
cosmologies and recent conjectures about quantum gravity.
