aramis erak
Legend
Plus the significant mechanical "mid edition course change" of Tashas essentially is already a stealth edition. Stealth editions tend to not attract more new-to-edition players (and corebook sales), and tend to drop off fans of the game before the shift. In the first case, because they get told the key is super important and should be considered core, upping the barrier; the latter due to any such element disappointing at least some fansI can easily see D&D sales taking a dip for the next 18 months or so with that dip just having started, as there's an announced new edition on the horizon which tends to kill off sales of the previous one.
Tasha's is only the latest of many such stealth editions...
AD&D 1's Unearthed Arcana
AD&D 2's Player's Option C&T and S&P.
D&D 4E's 4E Essentials
Star Frontiers and Zebulon's Guide
And, non TSR/WotC...
MegaTraveller's Hard Times
Pendragon 3e's Knights Adventurous.
Pendragon 4e's Book of Knights &/or Saxons! -- changes to character gen.
The One RIng 1E & Rivendell (tho' to a lesser extent. Really altered the metacurrency economy)
Every WWG WoD line and their Player's Guide. (Effect minimized by being quick out the gate after the core) Same for Streetfighter RPG.
Justifiers and the Corporate Handbook... total change in game focus.
GW's Judge Dredd and Judge Dredd Companion... not that it was well supported with adventures (grrr)... most were in WD, and reprinted in the JDC... Totally ups the game to a new level. Especially adding Judge Exorcists....