Marco is softening on Android, or at least developing an Android app for Instapaper. Or at least being open to the idea of it.
I can't afford to invest months of development time into learning the platform and making an Android app, then supporting and maintaining it in parallel with my iOS app indefinitely, with so many other data points telling me that it almost certainly won't be worth the investment.
He concludes with a challenge to Android devs to use the Instapaper API to create an awesome Instapaper app which he will bless as "official" and support.
Marco's reasoning for concentrating on iOS instead of all mobile is pretty obvious to anyone who has listened to the excellent Build and Analyze podcast.