Pulling the thread back a little bit...
I'm pretty confident that's *exactly* what they're doing. I strongly suspect that 5th edition is meant to be an on-shelf entry point and nothing more. I strongly suspect WOTC intends to "Unify" the player base by treating every edition as if it's in print, because you'd have to be insane to think you can unify all of the other players any other way.
Look at WOTC's statements this past year. Paraphrased, "We don't care which edition you play", "We're not trying to compete with Pathfinder", "We don't care if we're number one in [ICV2] sales". Let's be honest, those statements would give suits and marketing staff strokes. Unless there's a reason and a motive behind it.
WOTC's going to announce their intention to support every edition going forward with conversion notes and/or edition neutral material. It's the only thing that makes sense given what they've said, and honestly it's the only viable business plan at this stage.
Especially in light of the comments about keeping 4th edition in print, which makes no sense because it wasn't a big enough customer base to support the edition when it was "The" edition, why continue to sell it alongside 5th edition?
I'm strongly of the opinion that 5th edition's purpose is to provide an entry point, and perhaps a "Merge lane" where the different edition's players could play together if they wished without have to fight about which edition they'll play.
I think WOTC has a couple of aces up their sleeve they haven't played yet. I'm guessing it'll be revealed at Gencon but I suppose PAX is possible given it's popularity these days.
I agree in spirit, but differ on how I think they are going to execute it. I think the point of 5e is not to be simply an on-ramp, but also the medium through which WotC can address the market as a whole, rather than split it by offering products for each edition.
Emulation of previous editions via 5e allows people to buy it without invalidating much of their previously bought material. Got a lot of 4e stuff? Take 5e, jack up healing from rests and drop down short rests to 5 or 10 minutes, add tactical module and go to town. Have a lot of 1e or BD&D stuff? Drop healing from rests down, jack up short rest time to an hour or more, add exploration module and enjoy. In these kinds of cases, you'd simply use 5e monsters instead of the ones in the original, and use the adventure as a frame: labyrinthine dungeons for exploration in the case of old D&D, larger rooms with interesting terrain and features for later editions.
Going from the other side, they can design new adventures for 5e that can be used in other editions. Murder at Baldur's Gate, for example, was specifically written to be usable with 3e, 4e, and 5e. Steve Winter wrote an adventure for Dungeon 210 called "Blood of Gruumsh". While written for 4e, it's an exploration-heavy adventure designed to be used with older editions with a few alterations.
So, IMO, rather than full conversion notes for every adventure, past, present, and future, I think we're more likely to see general advice, probably on their website, for configuring 5e to emulate different editions and conversions of adventures.
The typical rejoinder to this is that if WotC wants to put most of their eggs in the adventure publishing basket, they're in trouble because WotC adventures suck. But just because they sucked once doesn't mean they always must. Late 4e adventures like Madness at Gardmore Abbey were very well received. It's probably fair to say that WotC has largely sucked at adventures because it has not been their focus, at least compared to splatbooks. If they change focus, they may very well change performance.