Microsoft is not saying how many applications will be available to WP7 on Monday through its online Windows Phone Marketplace. The question is an important one, since too few could spell disaster, Llamas said, pointing out that the Palm Pre launched in 2009 with only 32 applications.

"Microsoft deserves congratulations for 300,000 downloads of the developer tools, but I would hope they have more than the 32 apps that Palm Pre had," Llamas said. "They need a goodly number, although I don't expect 100,000."

Other than saying AT&T will attend the Monday event, Microsoft hasn't specifically named the first wireless carriers of its phones, although in February it called the four major U.S. carriers its "partners" in WP7. AT&T, a GSM carrier, is expected to be joined eventually by T-Mobile, another big GSM carrier, as well as Verizon Wireless and Sprint Nextel, which both run on CDMA.