Turns out I was partially right with my last prediction: soldiers and demos are competing for an item, it's just there's only one item at stake, not the whole update. (I wonder what they've designed that works for both classes? I've been meaning to write a post about how Soldier and Demo are mirrors of each other, like pyro/heavy, and Scout/Engie, but that'll wait for another time.)
You may be wondering how to win it for the good guys, the Soldiers. Mostly, just playing Soldier as hard as you can should work if you're good. Target Demos first, except for maybe Medics. (Come to think of it, targeting medics, then demos should always have been my strategy.) If it looks like a Demo has you cornered, jump into holes to your death, but don't kill yourself through the console or with a rocket if they've done any damage to you; they'll still get the kill. Play more carefully, if you're at low health, don't be afraid to let your team lose if it means not dying to a demo. If nothing else, try to get killed by
If you're not so good with Soldier, run Medic. If you want to be a team player, only heal Soldiers, never Demos. Try to take health packs before Demos can get to them, even if you have to get hurt to pick them up. Remember, the Soldiers on the other team are on your side too.
I wonder if Soldiers will get an attitude of just nodding to each other as they pass by. The only problem with that strategy is that any Soldier I don't kill could be killed by an "allied" Demoman. I've seen some Soldiers in good positions against Demos and just walked away, but I don't think we'll ever see a fully-fledged peace treaty.