There maybe a financial rationalisation in the future. Formula 1 and a support GP class. The GP class made up of 'Formula E, GP2, GP3' so only one chassis is required and perhaps an upper & lower grade for 2 support races, so the fast young racers get matched against each other in similar machinery allowing F1 teams to identify the better drivers.

As battery swapping technology gets better, we might see a battery pack swap for Formula E like a nascar/ le mans refueling stop. Tesla has already shown a demo of a battery swap quicker than a service station liquid refuel stop.
http://youtu.be/FE81S26XG8c (starts at one minute) Imagine the pit crewman halfway along the formula e car with a super dense battery on a flat jack swapping or adding another battery at the current F1 pit stop speed.