They might also get some new customers; I was considering an iPhone rather than Android in my last phone purchasing round, but no USB-C means I need different charging, means I don't want to deal with it. No headphone jack is also something I don't want to deal with, been there, lost the dongle, would rather not go there again.
Maybe in the US, but in the EU Android has like 70% of the market.
An awful lot of kit is already going to landfills due to being rendered useless for depending on non-standard components to work. Personally I had to throw out a couple of phones because their chargers stopped working.
Also, it's not as if lightning-to-USB-C adapters are unheard of.
To top things off, even if we somehow assume that USB-C is unable to meet anyone's needs in a few years, and in the process ignore the fact that USB-A has been meeting all needs for some decades now, why would we jump to the conclusion that whatever port format comes next it will be technically impossible to get it to work with USB-C, or offer it in parallel with USB-C?
If it was one of the dozen or so variations of little USB with 2% or 3% market share each you'd have a point, but those have mostly gone already.
I don't expect Lightning to be around forever, but then I don't expect USB-C to be around forever either. Some day it will be super-ceded - should be super-ceded.
Apple has shown remarkable consistency and discipline in managing it's connector designs. Far, far more so than any other manufacturer I can think of. They were also at the forefront of adopting USB-C in the first place and spearheaded making it so popular.