If you look at desktop market share numbers the vast majority of desktop users are using traditional desktops.  Just look a the Valve Hardware & Software survey.  This is a useful tool for gauging the #1 Student/Gamer user-base.

If we add up the numbers:

Windows 7 + Windows XP/Vista + Mac OS = 78% --- traditional desktops
Windows 8 = 20% ---   "mobile oriented" desktops
Linuix = 2% --- mixed

link: http://store.steampowered.com/hwsurvey

The same is true if we look at Wikipedia's "Usage share of operating systems" page using Net Application's statistics:

Windows 7 + Windows XP/Vista + Mac OS = 87.7% --- traditional desktops
Windows 8 = 10.58% ---   "mobile oriented" desktops
Linux = 1.6% --- mixed desktops

link: http://en.wikipedia.org/wiki/Usage_share_of_operating_systems

Abandoning Gnome 2 was a fatal error on the part of several high profile distributions such as Ubuntu and Fedora.  They abandoned Gnome 2 to chase mobile oriented ambitions when in reality the vast majority of Windows and Mac users were still using traditional desktops.  This limited the growth of the Linux desktop as a platform and caused unnecessary confusion and chaos in the Linux community.  Current Linux desktops that are achieving success such as Google's Chrome OS are still using traditional desktop design patterns.  

So that leads to certain questions for the Fedora Workstation WG as to what the scope of their project is. Does the Fedora Workstation WG intend on expanding their user-base beyond:

1. Fedora/Gnome developers and current Fedora users?
2. Linux developers and/or users?
3. Mac and Windows developers and mainstream users?

If the answer is: 

#1 "We only intend on targeting Gnome and Fedora developers" then make the default Gnome Shell and ignore Fedora.next and continue the methods and policies of Fedora Desktop and the spins as if nothing has changed.

#2 "We would like to consolidate the Linux desktop space" make the default MATE with Gnome Shell and KDE as optional extras at the installation screen.

#3 "We would like to market Fedora Workstation outside of the Linux community to Mac and Windows developers" make the default MATE with Gnome Shell and KDE as optional extras at the installation screen.

What would it take to get MATE up to current standards to be acceptable as a default for Fedora Workstation?

+ Have the Gnome project developers provide support resources to the MATE developers to accelerate their transition to GTK3 as well as act as consultants.

+ Perhaps even offer to make MATE part of the Gnome foundation as a legacy Gnome 2 fork and provide additional support resources? 

+ Configure a MATE desktop that is Fedora branded that uses default Gnome applications currently used in Gnome Shell such as Files and make sure it integrates with MATE.

+ Bundle MATE with a lightweight compositor such as Compton or integrate Mutter as a MATE compositing window manager.

+ Replace the default menu in MATE with 'mintmenu' a plugin that replicates the Windows 7 start menu functionality and add additional plugins where necessary.

You see it's not that much work at all and well within the scope of something achievable by a distribution with sufficient resources like Fedora and/or provided by Red Hat.  It all depends on whether the WG is serious about consolidating the Linux desktop, expanding to Mac/Windows developers and achieving the goals set out in the PRD.

I'm beginning to take a cynical view of the whole Fedora Workstation WG process, I don't anything will change and Fedora Desktop will continue to decline in relevance, but please prove me wrong.