well while there isnt definite *Proof* I think that having an entire blog entry from the soldier (along with weird references from the latest crossword blog )and him mentioning defending a hill twice might just be Valve hinting towards it. Valve has been releasing/announcing content in very unconventional ways, (take the spy update for example) that I don't find hints via blog posts to be out of the question, especially since it came from Valve.
Obviously I could simply be very wrong on all this but, you cant deny the possibility.