To continue his analogy with RSS, When Google killed reader, they did provide an option to export all your feeds. Several RSS clients came out, but RSS itself was under attack by Twitter, Facebook and co., and it never regained steam.

Ten years from now, unless you believe weblogs are going to die, I don't think you should be too worried about having Medium disappear and take all your writing with it. What incentive would they possibly have to not have an export option to let users take their content away?

As it stands now, they offer the best writing / reading experience on the web and while I'm all for competition and innovation, I'd be satisfied with their product even if it does not change for the next 10 years.