In the most recent Earnings Conference Call both JB Straubel and Elon Musk noted that the battery cells from the Gigafactory may be a different physical format from what is currently used in the Tesla Model S. That change in format will be to allow greater density of energy in a more efficient package, for use in the Model ≡. Even so, the Tesla Model S may continue to use the same size/shape battery cells that are currently supplied by Panasonic, but that doesn't mean they won't improve in energy density as well.
JB Straubel has stated before that even without a change in format, lithium ion battery cells effectively double in capacity every ten years or so. Even if the battery cells have only improved by 50% in 2017 from what was used in 2012, it will still allow a Tesla Model S to have perhaps a 128 kWh to 142 kWh battery pack with a minimal increase in weight. I predict they will have something like a 135 kWh battery pack for the Model S by then, and possibly a 170 kWh battery pack. I estimate that with a 135 kWh battery pack the Model S could manage about 421 miles of EPA rated range. That would climb to 530 miles or so with a 170 kWh battery pack.
I'm considerably more optimistic than most are about what Tesla Motors will be able to manage over the next three-to-six years.
Take a look at this thread:
The 500 Mile Tesla
I posted multiple times there about my projections, which are of course, almost certainly wrong. ;-)