There's no word on exactly why Tesla is making the change, but a similar process occurred when its larger battery option jumped from 85 to 90kWh late last year. Eventually the older battery was phased out and it wouldn't be surprising to see the same happen here, although for now Tesla says the 70 and 70D models will still be available. Combined with the recently refreshed Model S design and options like a faster standard charger, it fulfills earlier rumors of a slight price hike on the way, so if a few grand (or 15-20 miles of range) is enough to swing your next electric vehicle purchase, it's something to be aware of.