So, the original hypothesis behind dark energy was that an analysis of Type Ia supernovae showed that the expansion of the universe is accelerating - before that it was thought to be constant - in 1998. Scientists had to invent dark energy to explain why.
And now it's widely accepted and everyone is looking for dark energy.
Not so fast.
A much larger study of Type Ia supernovae has now shown that...oops. The accelerating expansion may have been a sampling error and the universe might be accelerating at a constant rate after all. (And the accelerating expansion theory won a Nobel - that's how good the science looks).
Which is it? There's going to be a lot more studies done before we work this one out. Oh, and apparently the universe is expanding faster than expected anyway.
So, what does it mean if the universe is expanding faster but not accelerating?
If expansion is constant, then the lifespan of the universe is longer than we thought. If expansion is faster, then we may have the age of the universe off a little (we're talking 5 to 9 percent here).
Oh, and if there is no dark energy then the chance that the universe will actually end in a big crunch (possibly followed by another big bang) is more likely.
Or they could be wrong. Either way? There is little more exciting than scientists being wrong.