Some things happen in a way that people don't actually go WOW! Although I personally was Wowed by the early 90s WWW, the populace as a whole was not immediately. Yet what more than the web has changed human society in recent times?

Possible 21st Century WOWs

+ Wacko hydrino (Blacklight Power) or zero point energy sources provide small scale distributed energy

+ Ultracapacitors or totally unknown battery technology allowing strong electrical storage >10x today's lithium ion batteries

+ Bussard Fusion allowing inexpensive small scale fusion power plants

+ Any type of propellentless 'space drive' (Drive, not solar sails etc)

+ REAL AI embodied in a way people can perceive and interact with

+ Receipt of interstellar radio or other signals from another tech civ

+ Personal genetic code analysis with readily available replacement of organs & subsystems

+ Virile ecosystems discovered under Europan ice or say on Titan

+ Continental scale imagry and active atmospheric biology detected via spectroscopy of a life bearing exoplanet

+ Maybe just for geeks, but definitive proof of the multiverse

+ Discovery of ancient ET technology in the solar system

Other than habitable exoplanet imaging and personal genetic code benefits both of which I'm confident WILL happen, the others are all long shots of varying degrees