I think the problem they are facing is one of not living up to what they said they were working on. They made it seem like they were working on an edition that would appeal to players of ALL editions, or any edition.
Now if they had stuck to a VERY BASIC version that allowed add on modules to make it more like a specific edition (such as one for 1e, one for 3e, one for 4e) and released the CORE book along with the edition specific module at release (so two books, one core, one for the edition type you like) I think it may actually have gone better thus far. They would have concentrated on the core rules that were very basic with explanations that this was ONLY the core...and then have playtests for different edition modules.
As it is...I see extreme problems with what they are doing. They've lost their way. Who are they trying to appeal to?
Old timers...they've lost over 20 million of them...do they really think they will get them back? If so...why?
I'm an old time player and this new stuff feels more like a 3e/4e hybrid than anything old school. HECK, the OSR movement meets old time gaming FAR more than anything Next has thus far. Next doesn't even appear to be TRYING to do anything to really appeal to those gamers from the 70's to mid 90s...or if they are...they need someone who actually knows that audience. They obviously don't understand the oldtime gamer or what they would be after at this point from what I'm seeing.
NONE...and I mean NONE of those that I know from my days of the 70s and 80s have any interest in this right now. Of course most aren't playing RPGs at this point either (in fact one just gave me some of his old D&D books). If they were to be brought back it would have to be simple, something that they recognized as D&D (which means, 3.X and 4e it is NOT), and something they'd want to play with their kids or grandkids.
For 3.X gamers...I've seen some interest, but it's dying and dying quick. Next has some items that resemble 3e and 3.5 (D20 universal for skill checks, less adaptability but there are skill and adaptability options), but overall...if they aren't still playing 3.5, they are playing Pathfinder. In fact, the group I play with currently seems to be all about Pathfinder. The big question is...why should they play Next instead of Pathfinder. Right now, even with the current iteration, there is nothing to be gained from switching. They are very happy and content with where PF is at, and see nothing that DD Next offers over PF.
For 4e, I'm not certain. There IS some interest with the 4e gamers I've played with. However, many think that there are too many steps backwards from 4e to older editions (despite that older gamers probably don't think it's enough like their edition) to really cater to them.
So the problem is, instead of doing what they intially stated they would do, they've actively moved backwards and are achieving the exact opposite of what they stated. At least from what I'm seeing. Instead of appealing to players of any edition, they are actually making a game currently that is of interest to NO players of any edition of D&D.
I don't know what the future holds, and thankfully they have a lot of time, but currently if it were to be released shortly instead of further along and what we have is an indication of what is coming...I'd say D&D NEXT would be an unmitigated failure at release.