To be honest, I think that you should concentrate on the aspects that employers want to see, rather than your own interest, because really AppGameKit developers have advantages over native developers.
I can code in C++ as well as I can in AppGameKit or DBPro - yet it still takes twice as long to do anything, and it's not like there's a world of difference in performance. A solo developer is much better off using AppGameKit, than native platforms IMO, I think they'd get a lot more done, and it's the idea that makes money these days, not the tech.
So, I would say you need to decide if your learning for your own development, or learning for a job with an app company.
If your not worried about potential employment, I would say that sticking with AppGameKit, but also looking into some HTML5 stuff is a good bet. Maybe even look into the engine that our old compadre Rich Davey has come up with for AS2... www.photonstorm.com
I think it would be cool to use AppGameKit for mobile platforms and rapid development, then port to AS2 for online versions.
I am the one who knocks...