This is the best bit of being a Team Fortress 2 player: the hints. It was fun to speculate about what new toys Valve might give the ninth class once they'd updated the other eight, but it's not until they start giving us clues that the ideas really start flying about. They put up a very brief teaser video last night showing the Engineer in his workshop, and in 26 seconds gave us at least five distinct hints about what they might be giving us the game's next big update.
1. Dispenser with radar.
This is unmistakably the Repair Node device Valve said they tried and ultimately rejected. It was a box you could take instead of any other deployable, and it would repair the buildings around it, letting the Engy roam free.
Valve scrapped it because whichever other building the Engy chose to sacrifice, it made him a worse team player. Is it here now just as a nod to that failed idea, or did it evolve into something that would avoid that problem? Valve concluded from the Repair Node experiment that "New buildings in the Engineer update will probably take the form of upgrades, or entirely new choices alongside the old buildings, instead of replacements." Perhaps the Repair Node is still in, but as a costly Level 4 upgrade for the Dispenser.
2. The metal head.
This is the big one. We see a smooth bronze dome in the foreground as the camera pans past, and when we later get a side-on view, it clearly has a single slit in the upper half, from which a flickering red glow eminates. It's hard not to picture it as the head of some killer robot. It could equally be a metal mask for the Engy or his team-mates, but the light in the visor slit is less consistent with that. Not much to go on in itself, and perhaps a total red herring, but then there's the...
3. Blueprint for a robot arm.
Whoa. This is the one thing in the video that seems most likely to be a real hint: blueprints are how the Engy places items in the game, and it makes sense that the blueprint on his workshop wall would be of whatever he's been working on. The question is, is this a cyborg arm for himself, or part of a humanoid robot? Valve snuck AI-controlled players into TF2 a while back, then quietly acknowledged them on their blog, but never really made a big deal of the addition in the way it seemed to deserve. Perhaps part of the motive for testing out and improving that AI was to pave the way for some kind of glorious deathbot the Engineer can take instead of his Sentry?
Update: Forumite Ritz has drawn a clear version of what he says you can see of the blueprint, and his diagram shows what's surely a robot leg next to the arm.
4. The legs and flamethrower.
The Engy is working on something with two legs sticking up from a grey chassis. They're the same legs his Sentries have, so he's almost certainly getting a new deployable weapon. In front of it, we can see the same gas tank as the Pyro's flamethrower - is this the much-suggested flame turret? The idea never made a lot of sense to me - fire in TF2 does attrition damage that's only a major threat if you can't escape it. If it were fired from a stationary turret, you'd always be able to get away. If our wildest dreams come true and he gets a murderous automaton, it could have a flame-based weapon. It'd likely be somehow different the Pyro's, though - after the recent nerf, that poor chap has a hard enough time without being replaced by a robot.