  We consider the fate of the observable universe in the light of the discovery
of a dark energy component to the cosmic energy budget. We extend results for a
cosmological constant to a general dark energy component and examine the
constraints on phenomena that may prevent the eternal acceleration of our patch
of the universe. We find that the period of accelerated cosmic expansion has
not lasted long enough for observations to confirm that we are undergoing
inflation; such an observation will be possible when the dark energy density
has risen to between 90% and 95% of the critical. The best we can do is make
cosmological observations in order to verify the continued presence of dark
energy to some high redshift. Having done that, the only possibility that could
spoil the conclusion that we are inflating would be the existence of a
disturbance (the surface of a true vacuum bubble, for example) that is moving
toward us with sufficiently high velocity, but is too far away to be currently
observable. Such a disturbance would have to move toward us with speed greater
than about 0.8c in order to spoil the late-time inflation of our patch of the
universe and yet avoid being detectable.
