Before I answer your questions, you should
know that I am biased. My career has been built on top of Android, so of course I think it's the future ;)
Android is the most popular mobile operating system. As it stands today, I think it's a safe bet that Android will be important for a while. As far as native/hybrid/web goes, I don't know what the future holds. It's been a dream for years and years that you can write your code once and run it everywhere. In my opinion, that dream isn't fully realized and the best mobile experience comes from native applications. Until that changes I am going to focus on Native apps.
I am also going to focus my time on learning Kotlin. I believe that Kotlin is the future of the Android platform.
I hope that helps. That's a big question. Feel free to post some follow up questions if you'd like for more of my opinion on other parts of it.