The real question is can they really not do it? Elon is the guy who can put rockets in space and electric cars on the roads, I'm sure that it is possible. Now do they WANT to do it, that is the better question. To that I would say I doubt it, they probably don't want competition for their charging network. Such as in places like Australia, where it now costs more to drive your Tesla on a road trip than a gas car:
Tesla Supercharging now more expensive than petrol refuelling
In the EU they were forced to do it by regulation, but I doubt we'll see that in NA anytime soon. The Chademo adapter is NOT direct competition to supercharging, it is too damn slow. However, a well made CCS adapter could be direct competition.