New electric cars will be capable of driving at highway speeds (with top speed up to a 100 mph) when they come out.

Range is a concern so range-extended electric cars (or series hybrids) may be more attractive over pure electrics.
On the other hand major automakers start to work with electric companies to research and develop an infrastructure for EVs. Mitsubishi teamed up with SCE and PG&E to test iMiEV in California; GM is also in talks with utilities on plug-ins; Nissan works in Tennessee. So it is possible that very soon there will be even less need for range extender on the electric cars. except, may be, for really long trips.