It takes time to transition to another API. DirectX 11 was available for a long but it's not until recently last year that every new game came supported with it. DX 11.2 is nothing but a small update much like how DX 11.1 was irrelevant. 

I really don't think this means what some think it means. Read the DF Architect's interview :

http://www.eurogamer.net/articles/digitalfoundry-the-complete-xbox-one-interview

"Digital Foundry: DirectX as an API is very mature now. Developers have got a lot of experience with it. To what extent do you think this is an advantage for Xbox One? Bearing in mind how mature the API is, could you optimise the silicon around it?

Andrew Goossen: To a large extent we inherited a lot of DX11 design. When we went with AMD, that was a baseline requirement. When we started off the project, AMD already had a very nice DX11 design. The API on top, yeah I think we'll see a big benefit. We've been doing a lot of work to remove a lot of the overhead in terms of the implementation and for a console we can go and make it so that when you call a D3D API it writes directly to the command buffer to update the GPU registers right there in that API function without making any other function calls. There's not layers and layers of software. We did a lot of work in that respect.

We also took the opportunity to go and highly customise the command processor on the GPU. Again concentrating on CPU performance... The command processor block's interface is a very key component in making the CPU overhead of graphics quite efficient. We know the AMD architecture pretty well - we had AMD graphics on the Xbox 360 and there were a number of features we used there. We had features like pre-compiled command buffers where developers would go and pre-build a lot of their states at the object level where they would [simply] say, "run this". We implemented it on Xbox 360 and had a whole lot of ideas on how to make that more efficient [and with] a cleaner API, so we took that opportunity with Xbox One and with our customised command processor we've created extensions on top of D3D which fit very nicely into the D3D model and this is something that we'd like to integrate back into mainline 3D on the PC too - this small, very low-level, very efficient object-orientated submission of your draw [and state] commands."

This is why we shouldn't expect miracles. Consoles always have good 'closer-to-the-metal' access to hardware, and of course this was a big focus when getting the XB1 ready. DX11 to DX12 on PC will be a pretty sizable leap in some areas thanks to things they've already done on XB1's version of DX. Microsoft have confused things with the naming, but think of it this way :

PC DX11 = DX11.

XB DX11 = DX12.

PC DX12 = DX12.

XB DX12 = DX12.1

The reason is that the big penalties with generalized hardware (draw call limits due to CPU) were ALREADY fixed on XB1. So the best we can do is look for tweaks in the area, but not miracles.

Why wouldn't the X1 have supported it ? After all it is MICROSOFT that CONTROLS the specifications of Directx.

"DX11.2 was released a month before the Xbox One.." - and DX11.2 was in development for how long??

Did you understand my long post or chose to ignore it with a snide remark? Do you know that DX<any version> actually consists of TWO parts, a definition and an implementation part? Even if MS did not have a low-level IMPLEMENTATION part of DX11.2 (or equivalent driver in X1's case), they had the finished FUNCTION CALL part (and at least a high-level implementation part) essentially finalised months, if not 1-2 years before the start of X1. Whether that was usable or not we don't know, and we haven't really heard anyone complaining about missing driver-implementaion parts.

That makes absolutely no sense ... 

The biggest reason for having dedicated handhelds are the tactile feedback of the controls on them. Touch screens are LOW QUALITY for gaming purposes compared to having buttons and other features of a gamepad. 

Indeed.

People really shouldn't read too much into the version numbers, because they simply don't line up exactly with what that would suggest.

The horse's mouth spoke in depth before XB1 launch, and they specifically said they implemented low-level draw call into XB1 from the get-go, something that simply isn't available on DX11 in any PC implementation. With Mantle, one can see the difference between a high-level generalized API that has the CPU bogging the draw call situation, and one that unleashes that a lot. Basically XB1 is already out of the gate with the optimizations in question.

HOWEVER, there is some room for optimism, on all of the consoles and the PC.

Reason? Games had to be in development long before the devs even had their hands on the SDKs (using PC). So the optimization, while available from day 1 on XB1 in terms of low-level API, almost certainly wasn't taken full advantage of. People had deadlines to meet, so much of the early titles (and even many still to come) simply had to be sloppily put together in terms of actually taking advantage of what the XB1 can do. The same is inarguably true of PS4 for the same reasons.

TLDR : Games will look a good bit nicer by this fall in some cases, but don't expect anything earth-shattering either.

This will have very little effect on Xbox One games, as consoles already have incredibly low level access.

PC however will see some pretty incredible gains from this if it delivers how they advertised it.

no games till 2016 that has dx12 features? great stuff!!!

"By “porting their Xbox One Direct3D 11.X core rendering engine to use Direct3D 12″ the small team at Turn 10 was able to replicate the same 60fps experience from Forza 5 on Xbox One and translate that to their PC demo."

So the X1 is working on Direct3D 11.X, not 12.

from what I see the big thing with Dx12 is the "console like API" on PC (especially better usage of additional CPU cores) and most of what is listed is a direct result of that

you don't need a new GPU with Dx12 compatibility, so there hasn't been much change there

the X1 already has a console API and devs already optimize for optimal CPU core usage