Seems that since about a week, this feedback request:
http://feedback.unity3d.com/unity/all-categories/1/top/active/editorgraphics-fullyfeatured-
Changed to started! I personally don’t need 2D but it will be a big step forward for unity. This probably won’t be in 4.x, but hey, still exciting!
Hmm, very interesting… And lets hope this Unity2D has Box2D built in.
Well i’d be damned.
I’m excited for this to happen.
Sure 
I know, right? I’d want it for menus, if nothing else.
And hey, perhaps this is the first step to a new GUI system.
I think it’s the other way around - the GUI system is their first step towards the 2D engine. They mentioned something along those lines at Unite
This is going to be a totally speculation-based thread, I can see 
It is cool news. However we have absolutely no idea of the scope of this. It could amount physics optimized for 2d plus some easy way to set a 2d camera plus some default sprite component that runs off a sprite sheet automatically… But if that is all? That’s far short of a full workflow.
2D level editing is far removed from 3D, as are the animation options.
I don’t see what it would have to do with the GUI system at all.
I really hope they don’t go down the every 2D game must use physics path… very restrictive. There are many other methods of handling and using collisions and performing animation. I also hope the tools that this brings are very WYSIWYG and not some horrible set of inspectors or scripts that you have to drag onto objects to activate or whatever. I want it in the scene view 100%.
I’ll be happy for anything that is made for 2D specific scenes. I don’t expect a full on 2D system. Although that would be nice 
+1
If Unity2D enables devs to make games like Knights of Pen and Paper better than Unity3D, what’s not to love? =D
I’m hoping this works like a new set of tools for dealing with 2D assets inside of the 3D editor, and that it’s not some separate 2D only editor.
I’d put my money into Box2D support. If you’ve been following Aras and Prime31 on Twitter you know there’s something happening (occasionally)
As for rendering 2D, they are going to use the GUI stuff for that, I have no doubt about that.
Since we are speculating I’m gonna make a prediction: Unity 4.2 contains this stuff!
4.5 is my guess
4.2 ha haha hhhaaa ha ha ah. I bet 5.x
When Aras has nothing to do it will come!
Agreed. A 2d/sprite framework will basically require everything a good GUI would need and more. If they were to release a whole 2d package and NOT have the new GUI already done, it seems like they would have wasted a whole lot of time and resources.
I’m really looking forward to seeing how this turns out.
Tell you what is baffling?
That the engine wasn’t designed with a 2D path from day one. 2D is 3D. It’s a whole consideration to make when doing “3d”. Every single 3D game will use masses of 2D elements in it. Text. Menus. HUDs. Overlay info. Billboards. Gui. The list goes on LONG BEFORE EVEN MENTIONING that there are more 2D games than 3D games made every single year by FAR.
So it’s a good step by unity, but a little late to the party. A lot of people use cocos2D / other libraries and shy away from unity due to the fact there’s nonexistent useful built in support for it.
I did TOB in it, but this is because I am committed at the moment, to the Unity platform and want to push it as far as it will go in respective areas. I have built our business along the Unity path. This might not always be the case, but for now I think it makes sense.
Would have made a lot more sense with very robust and very fast 2D support
Having said that, there are some quite-nice things about having a 3D engine behind it, depending on the game you’re making. Being too “2D” can screw up creativity.
Im looking forward to it.
Like some of the stuff discussed here: http://www.sizefivegames.com/2012/11/07/using-unity3d-for-the-swindles-2d/
I like the idea of a 2D engine, but I want to pick and choose what parts of the 2D engine I want to use. For instance, I use a perspective (3D) camera in my game for parallax and zooming, I’d love to mix it with a 2D Physics engine.
I hope, like others have said, it’s not a whole new product that forces you to be “TOO” 2D.
-Jeff