With the understanding that this is a single-source rumor whose validity I can't corroborate, I'd like to present some Windows Phone information that I know will be of interest to enthusiasts: While Microsoft, Nokia, and AT&T have all stressed that the Nokia Lumia 900 is "exclusive" to AT&T, none have stated whether this exclusivity is temporary or permanent. But according to my source, it is indeed temporary. And other carriers will be able to sell the device 45 days after AT&T's launch date of March 18.

Again, this is not a "fact." This information comes from a source at a rival wireless carrier and not from the Microsoft marketing documentation I've referenced repeatedly. I have not confirmed this with other sources.

According to this source, AT&T has a 45-day exclusive hold on the Lumia 900. After that time, other carriers can negotiate with Nokia for a version of the handset that will work on their networks. The source speculates that T-Mobile (and probably Verizon, possibly Sprint) will be getting some version of the 900 after it's been released on AT&T, most likely in the third quarter of 2012. 

These improved versions of the 900 will allegedly include an improved, 12 megapixel camera, the source revealed.

Why bother with such a rumor? I've received a lot of questions about whether other carriers in the US and elsewhere will be selling the Lumia 900. So far, Microsoft, Nokia, and AT&T have only stated that the device is exclusive to AT&T. So this information is, of course, interesting, assuming it's true. Take it with the necessary grain of salt. But that's what I've heard.