Oddly, I don't think i've seen a single explication of what the DnD Next developers mean when they use that term. And that deafening silence leads me, inevitably, to the conclusion that they may not actually know what the essence of DnD is.
Without a re-introduction of the essence of DnD, i'm afraid that the development of 5E will fail in one of its stated objectives: to end the edition wars and bring all DnD players back into the fold.
And honestly, it's not all that hard to discover the essence of DnD. One has to look no further than the plethora of excellent OSR blogs, and read some of the pre-1980 fantasy literature (those tales often referred to, by OSR types, as comprising Appendix N) to inform your understanding.
If the DnD Next designers need some further direction on where to start, I would offer up the following two resources: one, Chevski's article on Picaro and the Story Of DnD, and two, Clark Ashton Smith's The Tale of Satampra Zeiros. Those should give the DnD Next designers a nice, basic introduction to the essence of DnD.
Perhaps if they read those two items, and do further research thereafter, the designers of 5E will not fail the OSR.