ChromeOS has potential to become a productive platform. I don't really see Android ever becoming that. They are two different beasts.
iPhone development shares first party language support (albeit with some different frameworks) with a major desktop OS, and has third party support for a number of other languages.
Personally, I use my Chromebook for everything but serious dev work and photos & video work. Some of the things that I could not do on my phone/iPad that I use my Chromebook for are serious research, taking notes, watching movies in bed, using Google's Spreadsheets, minor dev via ssh and vim, and loaning it to guests and friends without a worry.