That was my thought, although it poses a moral conundrum.
If we suppose that Tesla Autopilot becomes so good that it would save X lives/year according to stats, would it be ethical to limit licensing to EVs only? Not only would this put ICE drivers at increased risk, it would endanger all drivers on the road if everyone did not have access to the best self driving system available.
But on the other hand, licensing Tesla Autopilot for use on ICE cars would prolong the use of ICE, which would potentially worsen the speed and effects of climate change. This will also kill people (through flooding, extreme weather, and tropical disease).
Good point. However, the other issue is that there will be and is competition out there. Mobileye, Comma.ai, Carnegie-Melon/Uber and who knows who else. So it will become an issue of market dynamics and competition. IMHO, there will be enough systems out there to cater to the ICE car makers.
So I think Tesla has a good marketing position to only cater to EVs if they want, since there will systems out there that will cover the ICE market. While we all believe that ultimately Tesla's home grown AP system will be superior we cannot discount the other competition, so I don't believe it will be much of a moral conundrum.
Ultimately all self driving systems will improve safety. Tesla pushing AP systems (with the jilted Mobileye crying foul) will help us all.