Sooooo, the Nexus 5 is now showing up on Google Play (name now confirmed). Tough to tell if this is an early mistake or something is about to go down officially. The price shows that it starts at $ 349 and there is a direct link to the phone (which is not live yet) that shows it will be a 16GB model. There could be a 32GB model as well, but that info isn’t available.
Update: And here is the mega-high-res version.
Update 2: The Nexus 4 is now completely gone.