But not to put too fine a point on it, but just ... well, just look-
Forgotten Realms
Nentir Vale
Dragon Fist
Thunder Rift
Ghostwalk
Planescape
Ravenloft
Pelinore
Council of Wyrms
Dragonlance
Birthright
Mahasarpa
Jakandor
Dark Sun
Eberron
Spelljammer
Greyhawk
Lankhmar
Mystara
Those are all full campaign settings that they haven't released yet for 5e that they could*, and this is before getting into sub-settings (Al Qadim, Kara Tur, etc.).
I like your list - and I'm for all of those being released too, and soon! The two Setting Search worlds would be in addition to, and perhaps after, the classic worlds are released. Yet so many people at ENWorld have called for "new worlds" - well, why not publish these two as-yet-unseen (and thus "new-to-us") WotC worlds?
Just to niggle with your good list: I believe Chris Pramas now owns Dragon Fist outright, so I think it'd take a license agreement to make the Tianguo setting fully a part of the D&D Multiverse. I might be mistaken tho.
And Thunder Rift is located (somewhere) on Mystara - it's a Mystara subsetting - even though it doesn't have an exact placement on the map, the two lead designers of Thunder Rift have said in interviews that it's located on either of the two unexplored continents of Mystara.
So ... it is REALLY HARD to get excited about a product no one knows about, that we can't even name, and was never developed, when there are already tons of campaign settings to use.
Well, I'm not asking anyone to get *super enthuasiastic*...just a little enthusiastic. C'mon, it'd be cool to see the "lost" Setting Search worlds.
Not to mention probably being able to easily license other classic settings (Wilderlands of High Fantasy). *I'm assuming; I don't know, for example, if they still have the license to Lankhmar.
Follow me?
Well, yeah WotC could probably make one-time agreements to do 5E conversions of Wilderlands, like they did for Kalamar, Diablo II, and Warcraft. But these are still "non-WotC" IPs--it'd take a whole nother level of doing to make one of these IPs a permanent part of the D&D Multiverse, and so continue to refer to those worlds from now on. WotC would either need to buy the IP outright, or make a special "perpetual license" agreement. I'm not so interested in just making 5E conversions without tying it into the D&D Multiverse. I mean, Judges Guild could make a 5E Wilderlands using the SRD, but it wouldn't be a part of the D&D Multiverse.
As for Lankhmar, I believe Pinnacle games is the most recent license-holder: Savage Worlds Lankhmar. 5E WotC products never refer to Lankhmar.