I'm interested to see what the underdogs will come up with. I'm keeping a close eye on Nokia and BlackBerry. My actual next phone will probably be an S4 (up from an iPhone 4) but I like trying new stuff and it's the underdog companies that are really innovating.
BB10 especially is of interest to me because of the gesture based interface. I liked that a lot in webOS so it's good to see it come back into modern smartphones. I wouldn't buy a BlackBerry today but I'm anticipating new interesting things from them in the future. I also hope they do a better job running Android apps on their OS in the future because that's a very important feature to gain marketshare and, well, actual app support.
The main issue I have with both BB10 and WP8 is the serious lack of customisation. Android is the only OS out there you can really make yours, the others just aren't competing in that aspect, which is a shame. Plus I'm guessing you won't ever be able to root BB10 with its emphasis on super security, which for a power user like me is a big letdown.
It's a shame because I want to try out new systems and I'm beginning to dislike Google these days, but the only mobile OS that really caters to my power user needs is Android. Maybe Ubuntu's new mobile OS will open up more possibilities in that area, only time will tell.