With Microsoft soon to be announcing Windows Mobile 7 at the Mobile World Congress in Barcelona later this month, there is high speculation that there will be a Zune Phone, model after the Zune HD, being able to play HD video straight out the box. Not only that, but be able to plug HDMI straight out too! I would think they would follow the Zune HD and make it via a dock connector of some sort, but we shall see. There has apparently been evidence of the existence of a Zune phone since the last update to the USB driver software. The phone will run the Tegra platform from Nvida just like the Zune HD does, so it may be the best screen you have ever seen! The idea seems that it will not be particularly a Zune phone, but a Windows Mobile phone with Zune software, much like the iPhone runs iPod software.
Here is a mockup: