What made me think it's fake the first time I saw it? Style.
The second paragraph is what got my attention. Damage centric role? Too much offence? Not enough Defence? If there's one thing Valve has been clear on in team balance is that they feel that the Soldier is the most balanced class of them all (I can't find the quote, but I remember reading it somewhere). "Default Offensive Stance"? I find that the Soldier is ALWAYS both OFFENCE and DEFENCE. He's one of those characters that tend to redirect the enemy's flow.
Also... the post is so vague. It's like, why bother with this post? It's a confirmation of the soldier, a confirmation of the item trade system, and a confirmation that they plan to make massive changes to the game engine so half the game population's clients and servers suddently have incredible new bugs and crash. There's not one solid piece of meat in that whole post. Valve likes to keep their hand close to the vest, but this smacks more of "I don't really know details" not "Neener neener, I'm already playing the update and you are not!" that Valve posts hint at.
"Breathe new life" isn't the phrase I'd use to describe what the TF2 mapping community needs. It's not like the community just stopped making maps. There's still new maps. "Enhance the community" or maybe "Excite the community." Bad writing style for a company who has their lawyers check over blog posts just in case.
And I seriously can't believe that the navel-viewing developers who gave us the "backpack" and "random item drops" would actually admit that players DON'T like having 7 kritz. I'm just sayin', based on the way they reacted to community unrest by claiming that all was going according to plan.
I don't know. Because I'm the type of guy who doesn't go pick up the newspaper without an escape plan, I'll give this a 90% Cheesiness Score. If this IS/WAS a real update, I can imagine it being yanked once everyone realized how badly written it was. People have mentioned that this is written in Valve's style; I'd have to disagree. It's written in a bad copy of Valve's style. Valve's style is much more humorous. Just actually read the real blog. The picture has a caption where the photographer tells the Solder to act natural, so the Soldier screamed at him to get a real job. THAT'S Valve's humor style, and I'd expect a little more of that in an Update Notification, instead of just using "Attention" and "Dismissed." I mean, come on, at least use DISS-MISSED!