http://www.theverge.com/2012/6/20/3096945/windows-phone-7-8-upgrade-no-windows-phone-8-existing-devices

Windows Phone 8 introduces support for multi-core processors, amongst other things, so the "Lumia 900 getting support for using dual-core or NFC doesn't mean a lot," says Sullivan, "because it doesn't have the hardware to take advantage of that."

Fortunately, I'm due for an upgrade this holiday season. Big Smile