77 or so million 360s sold.
~46 million Xbox Live members. (Including Silver)
~150 total million Sony PSN enabled consoles sold as of early 2012.
90 million total PSN accounts as of March 2012.
So yeah, there's a significant portion of consoles that could be connected to the internet but aren't. I'm not even going to start going into the reasons why (KennyParker did a great job already) but to say that people wouldn't buy a console but not have internet is pretty short-sighted. I know friends who don't want to pay the extra for internet because there's no benefit to them, they get Facebook for free on their phones and check emails on public WiFi.
I'm on 24Mbit/s and my internet is very fast for people in my largish city, every other internet connection I know bar the IT Techies is around 8Mbit/s or 1.5Mbit/s depending on which part of town they're in.
...The Xbox One won't play games if you don't connect once every 24 hours on your own console or once an hour on a friends.