3) There's nowhere near the infrastructure, bandwidth, etc. in place to allow for anything like 1080p downloads.
There's nowhere near the infrastructure or bandwidth for 720p downloads either if everyone were to start doing it, nevermind 1080p.
Anyone who thinks the immediate future is in video downloads doesn't know what they're talking about given the ISPs capping bandwidth and the idiotic DRM restrictions, neither of which look like they'll go away anytime soon. Maybe in 10 years or so when everyone and their grandmother has a fat internet pipe (yeah right), but I don't see downloads restricted to the device you downloaded them to (PC, DVR, iPod, whatever) catching on unless the electronics companies radically change how they approach this.