What are the technologies out there that may overtake the current battery technology.

The state of the art battery systems are looking very good and are using variations of the lithium polymer design. As for alternate systems current Hydrogen fuel systems are massively inefficient, though not in the way that you would expect. It is mostly in the creation of the hydrogen used. Splitting water (H2O) is an extremely inefficient and other than that it is extremely explosive (much more so than gasoline) and corrosive. The Fuel cells themselves still have heat and durability issues though I am sure that they will be resolved in time. Ultra-capacitors have shown promise, but still need a lot of development as they have a much lower power density and higher cost. They would be good for lessening the current spike when an electric vehicle takes off, but not really viable as a full power source.

I am holding out for lithium derived batteries to eventually come down in price and become common place in electric vehicles at least for mobile applications. If you are referring to large scale power storage, there are a lot more new technologies that are maturing like thermal, or water energy storing systems.