I'm not really worried about it.
I really enjoy my WP, and I don't think there are really any worries about it going away. I don't really care if it gets super popular or not. However, I do think it's inevitable that it will gain traction. Why?
1. Nokia is "all in." Therefore, we're guaranteed at least one OEM that will put its full marketing budget towards Windows Phone. I think Nokia will do for Windows Phone what Motorola did for Android.
2. Windows 8. The developer preview already has over 1 million downloads. And it's not even a beta. It's generating a lot of excitement and that will spill over to Windows Phone.
3. XBOX - The XBOX is getting a new Metro UI.
I actually think that if MS doesn't even do a big marketing push for Windows Phone, it's going to be big anyway. It will just end up taking another year or so before everything falls into place.