EV battery capacity is expected to grow to 100kWh.
People will park them at home every night, and probably somewhere with a charging point during the day.
Smart house energy management should be able to pick up on that usage pattern and use the car battery for the house while making sure the car is kept ready for use.
In the same way that wifi/mobile/satellite comms can keep us "always connected", the changes in power generation and storage are going to keep us "fully charged".
A house might use 20 to 30 kWh each day. Modern EVs have enough battery capacity to power some appliances for many days.
Vehicle-to-load ("V2L") is currently offered in vehicles made by Hyundai, Ford, GM, Volkswagen, Volvo, Mitsubishi and Nissan (the new LEAF).
Vehicle-to-grid (V2G) is more ambitious.
https://en.wikipedia.org/wiki/Vehicle-to-grid
The cost here is premature degradation of the battery due to additional charge/discharge cycles.