The two biggest mysteries in cosmology may be one. A new theory says that dark matter and dark energy could arise from a single dark fluid that permeates the whole universe. And this could mean Earth-based dark matter searches will come up empty.
While I'm somewhat skeptical of any hypothesis that includes a special/preferred frame of reference, the fact that this one simplifies things and seems to match reality at both local and intergalactical distances makes it very interesting. We need some type of testable new predictions that would fail for this hypothesis to test it against before we get too excited.