Did you ever notice this?

In the Dalek War Boxset that came out at the end of 2009, on Frontier In Space there is a trailer at the beginning before the menu, for doctor who dvd's both old and new. Well, I couldn't help but notice that there were clips from Terror of The Zygons (You see a Zygon attacking a UNIT soldier), The Greatest Show In The Galaxy (You see the doctor juggling in front of a book thats hanging down from the ceiling) and The Daemon's (You see The Master holding a pithfork like weapon and he's wearing a red/black cloak). So, why do they show you clips of stories that haven't even been released yet on DVD, not only that, those particular clips looked like they had pretty good picture quality as if they've already started to digitally remaster them, what are your thoughts on this?