MS already said WP is selling 4 to 5 times better than the same period last year.
And Comscore measures Windows Mobile + Windows Phone so their numbers are useless until there are no more Windows Mobile devices or they break it out properly.
Also, installed base is not a good way to measure current phone trends. Consider if everyone decided that their next phone was going to be a NextLatestAndGreatestPhone. It would still take 2 years for everyone to switch over to a NextLatestAndGreatestPhone and it would be a while before you even see any NextLatestAndGreatestPhones in the wild. That is with *everyone* switching.
I'm not saying WP is suddenly doing really well, I'm just saying keep these things in mind before jumping to conclusions.