Wouldn't Ubuntu Touch and FirefoxOS be competing in the race for 5th place? Windows Phone has third place locked up, and Blackberry is a very strong 4th place right behind them.
I doubt WP8 has 3rd place locked up. It's 3rd place, but it's a lot closer to 4th,5th, etc, than it is to iOS and Android. Blackberry and "strong place" don't match.
What would be the nearest 5th place contenders to WP8 and Blackberry?
WP8 has Nokia's entire product line running it. Nokia ain't what they used to be, but the brand still has fans and they make a lot of phones.
I think right now there aren't any strong 3rd place contenders. Windows Phone is the anemic upstart, BBOS is the swiftly declining dinosaur. Whatever the strengths or weaknesses both platforms have, neither have managed to project a truly compelling value proposition for consumers to seek out as an alternative.