The first batch will be of 10k boards. Will be sold out in a few hours...
Certainly I know friends who bought the fire sale touchpads, and many more who would have if they had the chance, none of which will be buying the raspberry pi - except the really techy ones.
Also, to do with the press it will get. Articles of "huge fire sale, get one while you can!" will be replaced with "this could change education" and "look what you could create with these" pieces.
Don't get me wrong, they will be hugely popular, and 10,000 is far less than the number of touchpads there were. It will also depend, obviously, on the per-customer limits they put in place.
I certainly expect them to sell out fast (will it be minutes, hours or days, I have no idea), but to compare the level of interest to the touchpad fire sale is huge exaggeration.
Using the camera and simple gestures (think Kincect 0.5) make an instant 'hangout' using G+ on your TV. Wave your hand, point at your circle, and blam start hanging out.
I've got like a zillion ideas of ways to turn a $35 board with HDMI+Networking into serious bank. I'm not unique in this regard.
Tiny full-fledged networked computers that are almost free they're so cheap will have a nasty habit of turning previous hardware into easily written software. The patent office/"industry" hasn't the slightest notion of whats about to hit them.
And in terms of stock and availability, to which the above is irrelevant, as I previously mentioned it depends on their per-customer limits, which I'm pretty sure will be in place (at least initially).