If that's the case, I'm not entirely sure that they'll be going back to the Great Wheel cosmology (they weren't, but the Outer Planes were at least going to largely resemble it, but this however really doesn't fit if that's the case).
It looks like they're trying to do some sort of compromise position here between 1e/2e/3e material and the rather divergent 4e redefinitions. I'm not sure how well that's going to work out.
To be honest, it could work out very well, or very poorly.
The great wheel is mechanistic (literally, but no pun intended!) and really the product of a dull obsession with symmetry even when it doesn't make much mythic/poetic/awesome sense. There's a lot of junk there (and I say that with love, not hate). I think all but the most extreme proponents of the great wheel would agree that it has it's flaws.
Similarly 4E, which whilst it was perhaps more mythic/poetic in it's setup, is flawed, and seemed a bit simplistic and obvious at times, without some of the high weirdness that was cool about the great wheel.
You could definitely take the best of both and come up with a default cosmology which was both far more poetic and exciting than the great wheel, but also less simplistic than that of 4E.
Similarly one could screw it up completely and bring in all the mechanism and boredom of the great wheel, whilst simplifying things 4E style.
Sadly we have a specific example of the latter happening, too - 4E's take on Sigil, which was horrifyingly bad. Inexplicably, they kept Monte Cook's unfinished mess of the Sigil changes, and thus kept the Factions basically exiled/gone (despite there being absolutely zero reason to continue that... continuity, in totally different 4E universe, I mean none whatsoever), and generally pared down Sigil, not to it's essential awesomeness, but to the very most simplistic take possible, and instead of the factions, the city was run largely by incredibly dull Three-Letter-Acronym organisations, like some sort of small city in the Midwest of the US (or some sort of middling corporation! No doubt the Lady of Pain receives her TPS reports on time!), rather than, y'know, the city at the center of everything!
So I can definitely see being worried about this. Whoever did that to Sigil in 4E should be kept the hell away from any D&D cosmology, I would suggest! I pray that they're not on the 5E team, but I fear that they are.