Almost every fundamental new discovery in physics so far has yielded great advances in technology. The exception seems to be general relativity - probably because gravity is such a weak force, it's difficult to make consumer items out of it.
I like to wonder what new technologies we could hope (in our wildest dreams) to obtain with a complete theory of physics. It might take a while, because we don't even know of any practical way of even getting experimental evidence for a grand unified theory so far, let alone make technology from those experimental results.
One possibility is new particles. Many promising theories predict various new particles. Unfortunately most particles other than the ones that make us up tend to be very short-lived and therefore don't yield any new materials. But if we do find a new long lived particle (and it doesn't cause a phase transition that swallows us all up) there is a possibility of new materials heavier, lighter, stronger or with better information storage abilities than the ones we have.
Another possibility is gravitational engineering. Particularly if we can find a way to violate the weak energy condition, we might be able to build stable, traversable wormholes, time machines and other such time/space abominations.
Even more far-fetched (but also possible) would be more ways to manipulate matter and energy, as in The Trigger and Ed stories.