They published this website (linked, via another blog post, from this announcement) a couple of weeks ago:

http://www.google.com/patents/licensing/index.html

And that in itself is just part of ongoing stuff coming from Google, so as you suggest this is not the kind of thing you throw together in a moment.

Having said that, once you've put in the months/years to get to this stage, you do get to choose the timing of your announcements.