Data by StatCounter suggests Microsoft's platform will be more common than BB by late 2012.
Windows Phone isn't a particularly fast-growing platform, but new figures suggest it is set to overtake BlackBerry in the US by the end of November.
This isn't due to any great step forwards by the Microsoft platform, but more because of BlackBerry's terrifying decline.
The projection is based on extrapolating StatCounter web usage data from the beginning of the year, and would mean there would be more Windows Phones in use in the USA than BlackBerries.
The reality is, this increase is probably going to happen even sooner, considering Windows 8 and new devices are expected for October, while BB10 is delayed until 2013.
With fewer than two per cent of US smartphones being Windows Phones, they'll still be be rare in the US; just not as rare as BlackBerries.