I just don't buy that this nostalgia exists for GH in a broad enough way. I see no evidence of it whatsoever outside of 40+ year-old players.
Borrowed nostalgia is totally a real thing, let's be clear. Everyone saw that recently with the '80s and Stranger Things and so on, but I think what you're not accounting for is that to borrow nostalgia you need a strong theme, strong visuals, hopefully strong sound/music, and so on, and GH has literally none of that. It doesn't have a distinctive and attractive associated art style (most of the borrow-able nostalgia-type '80s D&D art relates to DL or the FR). It doesn't have a compelling theme (nor does the FR, but no-one is trying to borrowed-nostalgia it!). It doesn't have music/sound people have already heard associated with it in any meaningful way.
You could do an "'80s D&D" push, but even then, the really big, memorable stuff from the '80s for D&D is all DL and FR.
There's no doubt some nostalgia for the start of 3E - though most players who feel that will also be 40+ now, because it's 21 years later. Those who aren't will be mid-late 30s. And I think Spiked Chains or similar idiocy probably have more tradeable nostalgia than GH from the 3E era.
None of this is to say WotC won't try to make it happen. They have an unfortunate history of failure in trying to make GH happen even when it obviously wasn't going to. They may well of course try to do what they did on the 25th anniversary and release a bunch of GH adventures, updated for 5.5E, and try to justify a 5.5E GH setting book with this, but unless they've done the update to end all updates, and one which will have 90% of people who "fondly remember" GH throwing tantrums, it'll be dead in the water.