To answer a broader question, will the proposed 2015 Super Charger infrastructure support Gen III. I believe the answer is no. 1) there will be minimally 100,000 units sold in the USA alone (and that is conservative) annually when Gen III goes into production. So, I do not believe there will be enough stations for the volume ramp up. 2) the distance between super chargers considering elevation and cold weather climate may be cutting it close for Gen III.
However, I firmly believe Tesla will increase the number of sites and expand the number of charging stations at existing sites after 2015. When Gen III comes out, the Walmarts, Costcos, Targets, commercial developers such as Simon Group, CBL Properties and others will want a Super Charger presence on (or expand at) their properties. Keep in mind if tesla sells power trains to another manufacturers and allows super charging, that is even more volume.