Just did a bit of number crunching, and there are 52 lineages/races released thus far by WotC that are neither in the 2014 Core Rules nor Mordenkainen Presents: Monsters of the Multiverse, while there are 50 lineages/races that are currently considered Core Rules or Rules Expansion lineages.
(This is assuming that Chromatic and Metallic Dragonborn were in the 2014 Core Rules, but have been overhauled by Fizban's).
I doubt we're in for another big book of lineages anytime soon (save possibly a M:tG one, see below), and most of these are Setting-specific lineages, but I think that 9 of these missing lineages will make it into the 2024 Core Rules:
1. Gem Dragonborn
2. 8 Tiefling lineages reflecting each of the other Archdukes of Baator
While Gem Dragonborn have been only very recently released, by 2024 it'll have been over 2 years, and I'm certain that other two Dragonborn sublineages from Fizban's are going to directly replace the Dragonborn breath weapon choices from the PHB. Meanwhile, the 8 Tiefling variants are the ONLY lineages from Mordenkainen's Tome of Foes to miss out on Monsters of the Multiverse, and I believe that to be because, minus their ability score modifiers, they'll all be options that Tieflings can take, rather than full-on separate lineage write ups like other subraces became in Mordenkainen Presents, sort of like how the three different Aasimar subraces were incorporated into the single Aasimar lineage (though unlike those, where you choose the angelic manifestation each time you use the power, I believe the Tiefling options will be chosen at character creation, functioning sort of like the huge list of Warlock invocations). I doubt that the Sword Coast Adventurer's Guide Tiefling variants will be in this book, though.
In addition, there are 10 currently-released lineages that are neither in the 2014 Core Rules or 2022 Rules Expansion that area already updated to the Post-Tasha's model (no ability score bumps). This leaves 35 lineages left unaccounted for as fully 2014-compatible rules but not fully 2024-compatible rules.
I don't think Tasha's Custom Lineage will be explicitly reprinted in the 2024 Core Rules as the 2022 Rules Expansion books are intended to serve as a companion to both the 2014 Core Rules and the 2024 Core Rules. But I do think it'll essentially be treated as an option for customizing your lineage, and the errata for the option already accomodates the lack of ability score bumps: it no longer assumes that the racial Ability Score bumps are in your race or lineage, but that IF a race or lineage has an ASI built in, you can replace it with another. This allows for the book to cross sub-editions of 2014 Core Rules and 2024 Core Rules, and let you modify the other 31 lineages that have NOT been updated, so as to make those 31 lineages compatible with the new revised 5e a decade into the edition.
Finally, of those 35 missing lineages, I expect several to get overhauled in future 2024-compatible books. Eberron is extremely likely for a setting revisit, and when it does, I expect reprints of Kalashtar, Warforged, and the Dragonmarked lineages (in addition to incorporating the Changeling, Shifter, Orc, and Goblinoid reprints, whether Keith Baker likes the Changeling changes or not).
There MAY be a big book of Magic: the Gathering lineages if there is ever a multi-setting-specific lineage book. This could reprint Loxodon, Vedalken, Simic Hybrid, Leonin, and Owlin, and I wouldn't be surprised if Reborn sneaks in there too as it really fits Theros' The Returned.
And Critical Role will likely get another official WotC-sanctioned book of options eventually. While Tal'Dorei Reborn is great for updating Tal'Dorei lore to the CR's 3th Campaign, it notably lacks ALL lineage rules - assuming that the player has purchases Explorer's Guide to Wildemount or some other book that covers the relevant lineages. Of the 4 missing Critical Role lineages, the Draconian Dragonblood/Draconblood Dragonborn and the Ravenite Dragonblood/Ravenite Dragonborn are MOST pressing for a rules update as they assume building off of the 2014 Core Rules Dragonborn and thus will NOT be compatible with the 2024 Core Rules, should it replace the 2014 Core Rules Dragonborn with Fizban's Dragonborn subraces as I consider likely above.
Planescape or Spelljammer is also a likely destination for setting reprints, if we get any of these 35 missing lineages/races reprinted before 2024.
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