I don't really disagree with your post, I'm just puzzled by your use of "need". How could WotC bring it about that thos who like PS need to embrace 4e-style eladrin?
Basically, default effects.
[sblock=sideconvo!] If you wanted to play the game that WotC is supporting during the 4e era, you're playing with elfaporting. If you DIDN'T want to play that game, no one's going to stop you, except the inertia and hassle of having to write over those bits of the game and/or prepare newcomers and/or the twinge you get in your neck whenever you open your newest D&D book and see bits about eladrin. It's a lot of mental effort to expend. ESPECIALLY when there's a competitor right next door that doesn't make you go through that mental effort 'cuz it doesn't presume you're playing a game with 4e-style eladrin ('cuz it doesn't have them).
5e can avoid that fate -- even with halflings! -- by ensuring that they aren't precious about their story. The drow don't have to be the drow in the PHB if they're drow from Eberron. The cosmology doesn't have to be the one from the DMG if we're playing a game based on ancient Japan. The story for genies in the MM doesn't have to be the story for genies in Al Quadim. Eladrin can be celestials in 5e Planescape and feywild elves in the 5e DMG. 4e went the other way (which has some branding benefits): eladrin are always the same thing, and are always present, unless you make the effort to exclude them.
I don't really like halflings in my D&D. In over 30 years of GMing I've been lucky to have no halfling PC since about 1984. I've GMed Greyhawk campaigns for years and never used a halfling NPC that I can recall. The fact that the mecanical systems I've used (AD&D, Rolemaster) have presented halflings as a default part of the campaign world hasn't been a problem - I've just disregarded that suggestion.
Now if a player wanted to play a halfling of course I'd have to grin and bear it. But that wouldn't change if the halfling appeared buried somewhere in an "optional" part of the DMG. The DMG can label something optional, but that's of little relevance when it comes to a player and GM compromising over what story elements will be part of the game.
Sounds a lot like halflings are a nuclear option in your games (as
David Noonan, one of 4e's big brains, goes on about here): you don't want to deal with it, your players respect that, and no one plays one, and everyone has fun. Halflings don't add to long-term fun around your table, to cop Noonan's phrase.
Clearly, if you're designing a game, you want to avoid introducing things that don't add to long-term fun around the table. And you want to keep things that do add to it! Halflings have been shown to add long-term fun to a lot of tables (they've been in the game and reasonably well-liked by the players since OD&D), so for the designers, you'd probably want to consider keeping them in, even if some players hate 'em. It's clearly not much of a deal-breaker for current players, and a lot of people have fun with 'em! But elfladrin were a gamble at 4e's launch: maybe they'd pan out, maybe not. And by removing other options to make room for eladrin, they were telling players who wanted to play the game supported by WotC that these eladrin should add more long-term fun to your table than the options they removed.
Turns out, they were right in some places, and wrong in others. And they were wrong, perhaps predictably, in regards to a lot of "hardcore" D&D players, who left for PF or the OSR. And where they went, people down the pyramid followed, because network effects.
If GMs don't like eladrin, just don't use them! If they have players who nevertheless want to play them, it seems to me to make no difference to those negotiations that WotC put the rules for them on this page of this book rather than on that page of that book.
To me, it's less about the page of a book (though that is a bit of it), and more about an attitude toward remixing. Historically, part of the big appeal of D&D has been relentless and creative remixing of fantasy tropes. Conan and Aragorn and Merlin and Elric go explore the Land of Oo and punch out Cthulu and everyone's having a good time. 4e, especially in the early days, took a more brand-focused view of what, say, an Eladrin could be, and this was speaking for the whole game, far and wide. Eladrin had One True Story, and it was important that no one attempt to redefine them, officially. And 4e did not. I believe if you looked through everything ever printed for eladrin in 4e, you'd find that it was consistent and unilateral and definitional.
At an individual table level, sure, do what you want. But when you're working against the system anyway, you can compare the systems that make it easier or harder to work against them. 4e told you how you should play guitar. PF was a lot more open to whatever you wanted to bring to its hippie drum circle. You could play whatever kind of elf you wanted to in either one, but only one was going to tell you that you were doing it wrong if you didn't do it their way. The other one passed you the OGL and told you to have a good time.
I must admit that 4e wound up as my game of choice in part because I'm a contrary, stubborn bastard.
[/sblock]