I actually agree but I think it's quite a narrow thing. Half-Orcs are an interesting thing to mention because I think they're one of the more "vulnerable" races in current D&D, as they have a less distinct identity and hit less archetypes. Halflings are just barely iconic/popular enough to keep blocking Goblins. Goblins, in general, are seen as more mischievous than outright evil, note, especially among younger players (in my experience), and double-especially among people whose primary experience of Goblins comes from sources other than D&D (where Goblin-type races are wildly more common than Halfling-type ones).I'd be shocked if goblins replace halflings, they're pretty iconic to D&D. Sure they overlap in being small and kind of sneaky, but goblins are kind of the grittier, more neutral/evil choice for sneaky characters. Like how the half-orc is for fighters/barbarians.
I think they'd already have replaced Gnomes with 5E if it wasn't for the fact that Gnomes are kind of the only clear "Smart guy" archetype in modern D&D (Elves sorta hang around there but it's not been primary thing since 2E High Elves/Grey Elves really).
I think going through the races of D&D and exploring their archetypes would be entire thread of it's own, but certainly I would say the most vulnerable 5E race for replacement is Half-Orc, closely followed by Gnome, more distantly trailed by Halfling. I think Half-Orcs could be replaced in the PHB by Goliaths or Warforged or a number of other races (including actual-Orcs) and there would be very little outcry - indeed I suspect such a replacement would please more people than it upset.
Half-Elves should, in theory, be vulnerable, because basically they don't do anything humans and elves don't do and the half-race thing isn't like, particularly attractive in and of itself, but they're wildly popular, and have been since at least 2E, and sort of carved out a schtick of "The key benefits of Elf plus flexibility and a lack of elven cultural baggage!"/. that you get to pretend your superhuman, great-looking, long-lived self is "trapped between two cultures" and thus some sort of implausible "underdog" despite their manifest advantages is just gravy.