PC Magazine notes that since Windows Phone was first launched, there haven't been a lot of new models. That is probably because most manufacturers and carriers, after launching the initial round of phones, were waiting on sales figures to determine when and if it was worth coming out with a new model.
At the end of the first quarter, Windows Phone had sold less than 5 million units since it was launched in October. When you spread that out over at least nine manufactures in dozens of countries, the sales per company get pretty thin.
While companies like Samsung, LG, and HTC aren't ready to get out of the Windows Phone market, if the platform folded their sales wouldn't miss a beat since they are enjoying far greater sales with Android. Even Samsung's own Bada was shipped on more phones in the first quarter of 2011 than Windows Phone did.
Nokia, on the other hand, has bet the farm on the platform. It will need to keep things fresh on the hardware side to generate enthusiasm for their devices. Say what you want about Nokia, but they have had some interesting designs over the years, even if powered by the uninspiring Symbian platform.
While a new phone every few months isn't new for Nokia, phones with a CDMA radio will be. Nokia has traditionally focused on GSM networks used by T-Mobile, AT&T, all carriers in Europe, and most carriers in other parts of the world. CDMA does have some strongholds though, and the U.S. is one of them. The largest carrier, Verizon, uses CDMA as does Sprint, and Nokia plans on supporting that technology, which means any carrier in the U.S. will be able to sell a Nokia phone, and that is what Microsoft and Nokia want to see happen.