Ask HN: Developing for Windows Phone 8

I'm currently developing for Android only and I'm thinking about starting WP8 as well but I have a few questions and doubts.

The reason I'm hesitant is because Microsoft announced the release of Windows 9 next year and I'm not sure about their plans for the current WP8. I don't want to waste time on something that has the potential of becoming obsolete.

Do you think it's worth learning?

How are the docs and API compared to Android? Is there something like SO for WP8?

How are the dev tools?

What's a good testing device?

I'm doing this as a hobby only and don't want to make it full time. I'm won't (and probably never will) do iOS, right now the reason being cost.