Battery tech will not reach oil parity within the decade. Oil parity would be batteries with roughly 1/3 the energy density of oil (maybe 1/4 if you factor in the fact that electric motors are lighter than ICE motors).

Predictions are hard, but I'm going to go on the record (and am willing to wager) saying that the batteries in EVs produced in 2012 will have an energy density lower than 9MJ/L.

Ultimately that doesn't matter though. The ED in the Model S is already almost good enough, it's the cost that matters, and I think that will go down. If you end up having a car that is a bit bigger and a lot heavier than an equivalent ICE car would be, you can still sell it.