From what I know, yes, they are working on it, originally called Progoton filesystem which was seen in the Microsoft source code headers. It's now called ReFS I believe.
I've already tested it as well, you can test on Windows 8 with a few files.
Also the minimum volume size supported for protogon is exactly 512Mb, whereas I believe NTFS is 256Kb. Bootcode is not supported yet, from bootsect.exe complaining. Meaning it's not yet possible to boot directly from a protogon/ReFS formatted volume, and the size of the system files seems to be less than on NTFS, and giving more available space on the volume to your own files from the get go. Very sketchy from when I first gave it a test though.
Remember the protogon system actually started when Windows 7 came out. Some of the headers indicate the protogon filesystem already existed, but it was NOT being used at the time. With this new concept though, more time taken can't be a bad thing, I would advise them to do so, without taking the marketing standpoint of taking extra time into consideration (as that would be a negative to Microsoft), as it means they have more time to perfect such a new implementation.
There's encryption abilities in this new filesystem now named ReFS as far as I know. I have seen Windows source code, and it does seem they have been working on this for some time now.
By Windows 9, if that's what they call it, i'm very interested in seeing what that has in store, as the protogon filesystem (ReFS) will surely be ready for consumers by then. However, also plans for 128 bit, which is being developed for backwards binary compatibility with as far back as 32 bit... Perhaps they will adopt the Windows 7/Vista style again? (I hope) as I don't want to be forced to get used to this new Metro for a desktop computer all throughout my future with Microsoft Windows. I'd gotten so familiarized with Windows 7 finally, and I personally think it's their best design yet.
Edit: Although the fact that they discretely included ability to use those dll's for the bluprint to format with ReFS/protogon, and not having it perfected quite yet, (even filesearching is flaky,) leads me to believe that they want others to perhaps be testing with it (devleopers (for now anyways))? By the official Windows 8 release, the question is, will they have completely figured it out though? Will they be forced to release it with a few very very minor bugs because of a marketing deadline? To be perfected in Windows 9? These are some things that will be interesting to see later on. I know everything is not about the programmig for them, marketing comes #1 always. Thus sometimes these small bugs are forced to be fixed through Windows updates at a later time