There has been a lot of recent discussion on a kind of "hyperdrive" space propulsion system that might be a possible application of Heim Theory, a theory of physics that at least partly integrates General Relativity and Quantum Mechanics. Burkhard Heim's theory is complex, relatively unknown, and not well understood by most physicists, but it has had some success in predicting the mass of certain fundamental particles. The recent paper (PDF) that describes possible space propulsion applications is what triggered the flurry of discussions. I've read it but I can't say I find it really compelling - to be honest I can't say I really understand it!
Although aspects of this proposal are testable, there is a heavy aspect of "if it really turns out to work this way" in it. But physics is by no means "complete" and maybe Heim Theory is part of the next step in understanding the Universe. I certainly hope it's valid and that it leads to a propulsion system that can get a ship to Mars in five hours. It would also be nice if it leaves the space-time continuum pretty much intact for the rest of us. There's a good overview on Damn Interesting.
Less dramatic but still pretty amazing is a breakthrough in ion engines by ESA and ANU, reported on Space News Blog. By decoupling the ion extraction and acceleration stages of the engine, much higher acceleration voltages can be achieved, and the test engine produced an exhaust velocity of 210,000 m/s, over four times faster than current ion engines. Thrust is still low, but the design is also much more scaleable than previous designs, opening the possibility of using ion propulsion even for large planetary spacecraft. There's much development to do, but this is an exciting development!