After speaking with no less than five different sources with knowledge of the matter, I am ready to confirm that the LG-made Nexus 5 should be unveiled later on today, along with Android 4.4 KitKat, additional details of which were leaked last night by former WSJ reporter Amir Efrati.
It's also likely we'll get the 4.4 SDK drop and see a major Wallet announcement, which aligns with the information in Efrati's documents and earlier sleuthing by Geek.com.
I'm hearing the embargo is officially lifting at 11am Pacific, but the announcement and possible Play Store availability could come earlier, so I wouldn't leave anywhere starting right about now.