I believe it was more than two or three months ago since we heard of it. I'd say the ps3 slim take the "worst kept secret" award of the year.
regular PS3's everywhere are already selling out because of the new price point. i can't imagine how much the ps3 slim is going to sell. i knew this day would come, sony will now catch up to the "other" consoles.
p.s. There are rumors (http://brutalgamer.com/?p=10977) going around that backwards compatibility will come once the god of war pack launches. it will include the original god of war, god of war 2, and the highly anticipated demo; god of war 3.