I was almost inclined to be drawn into the conspiracy theory-esque stupidity as I was reading the post as a whole. But by deconstructing each of the points brought up, the whole thing just doesn't put up enough valid arguments to fully convince me.
Bear with me as I try to analyze each point:
(There's less clutter if you just go to the other page instead of me pasting his list here)
1) This is pure speculation plain and simple. Once the update is released we'll see exactly how Valve decided to implement the mechanics of the new weapon. But to say that it's not real just because you can't fathom how the new weapon will work is not relevant.
2) Although the slight lack of quality does concern me a little, why would Valve deliberately make a low quality photoshop image and expect it to be a HILARIOUS dupe. And considering that Valve bases many of their in-game weapons and items on their real world counterparts, is it any surprise that the new baseball would look like a real baseball?
3) This one is just another Photoshop argument. I'm sure Valve uses higher res models and plenty of photo compositing to create their presentational artwork instead of just screen capping in-game shots. Also bringing up people's inability to handle the Scouts speed and lag is entirely subjective. But just because "a lot" of people can't handle running the game doesn't mean Valve is going to sacrifice the quality of their game just to cater to the lowest denominator.
4) Valve put out plenty of trailers which showed off all sorts of assets before the release of the game. Also, if Valve is supposedly not the type to hint, why are they being so hint-y at this whole alleged practical joke.
5) This one I can't argue with because I don't frequent those message boards, but this is one of the main reasons why companies refuse to accept "awesome" game ideas sent to them. Everyone thinks they're such geniuses to the be the first ones to think up of these great ideas. But the reality is that much smarter people who already work in the industry have plenty of similar and better thought out ideas already that have yet to be implemented through actual dirty work.
6) More subjective opinion that doesn't mean squat in why this would be a dupe.
7) This, I can't explain. It was what almost convinces me. A little.
8) Now this point is also very suspicious to me. But perhaps, the Scout update is not at the official steamgames page yet because it's not released yet? I didn't pay attention to the previous pending releases.
9) Valve shooping skills have been suspect in other featured pieces of"art" so again this doesn't is on par with expectations.
10) Nothing but invalid speculation here.
As much as I'd like his idea with how it could be a Spy update, none of the observations really hit anything relevant.
And he also ends the post with the classic conspiracy theorist claim of simply being someone pointing things out leaving it up to readers to "believe or to reject the ideas" that he offers. Sign of a pathetic grasping for straws. At least man up to your statements if you put them out there.

The update got released.

it was an early birthday present for me

Nice! Does this mean that the games will be flooded with Scouts running around trying to do weird things instead of helping achieve the goals?

yes.

I have yet to obtain the Medic acheivements. When the first update rolled out, I just refused to play Medic on principle, but then I just never got back around to doing the achievements.
I just strongly feel that achievements should be earned by just playing the game legitimately. If I happen to be rewarded for playing well, then that's a bonus.

I enjoy the crazyiness of these updates, they change the way the game is played for a week or so. Everything quickly goes back to normal after a while but while it lasts its normally fun. I have yet to get this one working properly, but the heavy update was good fun with 8+ heavys on either side blasting hundreds of rounds out.

Yea, the game got Hi-def models that you have to use the console to get.
I'm not all that sure about visual difference, but theres a folder for 'em in the resources.
Edit: Yup, more polys allright. There's also ways to go above "very high" regarding textures in options.
What I want confirmed, is that, I heard a rumor that valve will release the source engine update that lets you make stuff as good as "meet the ..." called source filmmaker or something.
Look, I dunno anything about it, and I only heard about it. So if anyone knows for sure, do say!

I agree with that, I don't have any of the upgrades, granted I don't have time to play that much, but when I do I play as whatever I feel is needed in the team.

Each to their own.
As long it ain't hurtin' anyone.

Right, as long as they're not hindering the game I don't care at all if they want to get the extras, more to them. But when there's 7 pyros in one team of 9, there's something wrong there, they should take turns at least, like each game some are pyros while others aren't. Although I have to admit that it sometimes is fun to play in bizarre games like that.

I don't so much have a problem with people experimenting with different strategies by employing an unorthodox number of certain classes, as I am opposed to people all going one class because they're oblivious to the needs for the situation at hand.
Sometimes it's hilarious and effective to have certain combinations. Like going all Heavies, or all Heavy and Medic combo teams, or this one time to mess with the other team, we went all Spies on defense.
As for the high poly models, I thought I heard a while back someone saying that the only parts that had more polys were in the face and hands? Supposedly, they were for use in the prerendered shorts.

I think the difference inbetween then highpoly models and the ordinary ones... is so little its not worth it.
Also, faceposing is borked up on the HWM models.
Personally, I prefer my TF2 looking like this:
http://img27.imageshack.us/img27/5391/cpwarpath0029.jpg
Yeah sure, I COULD run it at the highest settings, but when it looks like this... Iunno. It just looks better.

OT
Hehe, last game I've noticed this phenomena in was Red Alert 3. It looks sooo much better on low than on high :D
/OT

Check out these low poly models that some guy made. Quite beautiful in the way he distributes the polygons while still capturing the style and feel of the original characters.
Also speaking of graphical quality, it reminds me of the "hidden" ultra high settings that someone posted in this thread here. Honestly, I thought I was a graphics whore, but that's just a little extreme even to me. For a game like Crysis or Half-life 2 where the style is based more on realism it might be worth it. But TF2's crazy broad strokes and over-the-top art style just doesn't really call for that much attention to such crisp texture resolutions.