I have a buddy who works at a Microsoft Store. A few years back, he used to be obsessed with Windows phones and the Lumia line. Would never shut up about them and constantly tried to convince me to switch. Always gave him reasons why I wouldn't try their OS, and his response was always "Something big is coming, trust me." I wonder if this is what he had meant.
Maybe bigger screen. 6 inch display with a really high Megapixel camera. That is my guess.