Back in June, Valve announced a major balance patch was in the works for Team Fortress 2. A release date wasn’t given and, technically, it still hasn’t been - but Valve do seem insistent that it’s coming very soon.
In a post to celebrate the ten-year anniversary of the Orange Box, which first launched Team Fortress 2, Valve say they are “putting the finishing touches on a mammoth new update, and it'll be shipping in the very near future, we promise. How near? Well, very. Imminent. Not this week imminent, but you know. Really soon.”
So, still no date, and not this week. This month? Fingers crossed.
The scout and the spy are seeing some of the most attention in the rebalance, according to Valve's announcement in June. Scouts must now deploy, rather than simply carry, the Atomiser bat in order to benefit from its triple-jump ability, and it'll suffer a deploy time penalty to prevent quick switches. The spy's Dead Ringer cloak meter will also no longer refill at ammo kits and dispensers, meaning they won't be able to use it as often.
For full details of the balance patch, see this post from the Team Fotress blog.