Do not be alarmed -- these aren't really happening.
What you're seeing in the datamined files are tooltip updates. Steady Shot and Cobra Shot have always been 2-second casts. They are right now. Aimed Shot is indeed currently a 2.9-second base cast. And Chimera Shot does indeed do nature damage already. These are not changes to hunter abilities, but just the files finally catching up to report correctly on the way it's always been. Also the Kill Shot change is also a tooltip update rather than a buff.
The only change so far is the increased attack power for melee folks from our Trueshot Aura buff, as well as from all the other classes that provide it -- oh, and the addition of a nice endgame raiding gun, at long last. Assuming it doesn't later turn into a crossbow or daggers or something.
Brace yourselves for what could be some of most exciting updates to the game recently with patch 4.3. Look at what's ahead: new item storage options, cross-realm raiding, cosmetic armor skinning and your chance to battle the mighty Deathwing -- from astride his back!