Will there be a restoration nerf?

Probably not.

What about their dominance in 2v2?

You haven't been reading my blog, have you?

Essentially, we can boil the situation down like this:

1) Does Blizzard claim (or actually) balance the game around the 2v2 arena? No, they don't claim to and I have not yet seen any action taken against something that is quite clearly overpowered in 2v2 and mid-grade in 5v5.

2) Does Blizzard think druids are balanced in 5v5? Well, it's hard to say. Patch 2.3 yielded some unexpected changes for restoration druids in all settings, but primarily the 5v5 setting. Does Natural Perfection help in 2v2? Sure. Is it obviously the best thing since sliced bread with one guy beating on you? Yeah. Do you see improvement from one rogue beating on you to three rogues beating on you? Not a chance. Did Blizz accidentally buff restoration druids more in the 2v2 bracket than the 5v5 bracket with patch 2.3? You bet.

3) Will Blizz buff feral/balance/resto in 2.4, if so - how, and if not - why?

Oh man, that last one is hard (and I came up with it...)
Okay, well I would expect that feral and balance will get buffs. Their representation in 5's is so small that it's hard to deny that they need buffs. This will also, most likely, affect 2v2 and 3v3 play as well (which I care more about). I listed some buffs I'd like to see below this post, but I'm guessing none of them will be implemented. Maybe the Nature's Grace proc knocking the gcd down 0.5 seconds too, but probably not. More likely, something weird will be put into place along the lines of the 2.3 buffs to ravage and ambush.

Those were randomly added for unknown reasons. Look, if we wanted to improve the state of those specs, we should have buffed shred and backstab instead. However, I like the vein that Blizzard is getting in to. It seems as if they are beginning to recognize fundamental flaws in base class abilities, and are buffing them accordingly. 2.4 is SUPPOSEDLY about PvP balancing. Sort of a "class-review" for all classes (if anyone besides me remembers those days).

What about resto? Well, my guess is that perhaps certain things will be tweaked, but we won't see any real buffs or nerfs in 2.4. Blizzard seems entirely petrified at making changes that will potentially cripple or invigorate a currently strong class/spec. Although, we may see some changes after all, because 2.3 showed the Natural Perfection change; something aimed at buffing 5v5 prowess, and accidentally buffing 2v2 survivability more. Maybe that will be reverted and I can go to an x/y/31 build. Maybe Tree of Life will get some PvP buffs...