Nokia and Microsoft today announced that Windows Phone 7 would become Nokia’s primary smartphone OS, but that doesn’t mean the end of Symbian … yet. “We will continue to modernize the Symbian experience with selected UI enhancements and development of applications in Qt, as well as platform development work that is ongoing. This is important work to make Symbian more efficient and to protect our installed base of 200 million users around the world,” Nokia spokeswoman Laurie Armstrong wrote to us.Still, though, it’s looking like Symbian’s days are numbered.“It’s a transition program. It is Symbian people literally today who are working with Windows Phone technologies to advance those technologies. It’s a transition from Symbian to Windows Phone,” Nokia CEO Stephen Elop said.