Windows Phone 8 is here, but it hasn't made that much of a wave in the market yet, and now Sprint are looking to not even bother selling any Windows Phone 8-based devices this year at all. Sprint are reportedly waiting it out, until next year, to see how Microsoft's latest mobile OS is received.
TechCrunch have reported that the US carrier is waiting to see if Windows Phone 8 is worth the investment, but haven't released an official statement just yet. They could be delaying it for their $20 billion acquisition by Softbank, and don't have the time or money to invest in a yet unproven platform, especially with iOS and Android are already so strong.
Windows Phone 7 wasn't received that well compared to the mobile OS competition found in Google and Apple's offerings, so Sprint are probably just playing a waiting game. I don't blame them, and I would be doing the same thing. If there was an absolutely killer Windows Phone 8-based smartphone, like the iPhone was when it came out - then that would be different. As good as the Nokia Lumia 920 is, it's not the absolute be all and end all of smartphones.