But... there certainly could be a ton of evidence establishing a decade-long best buddies friendship between Trumpedo and Epstein, and such a revelation would make it impossible for Trumpedo to continue to claim it was all a "democrat hoax."

A "ton" of evidence? How likely is it that there could be a "ton" of evidence establishing a link materially beyond what's already been disclosed to the public? It's incredibly unlikely that there's anything that would be more damaging to Trump than the widely available photo of the four of them together:

media.gettyimages.com - From left american real estate developer donald trump and his girlfriend former model melania

...let alone anything that would establish that they were "decade-long best buddies." Especially since that would be utterly inconsistent with the entirety of Donald Trump's public life - he's a man who doesn't have any "best buddies friendships" with anyone. And especially since nothing like that was revealed by the Biden administration....or by either the Biden or Harris campaigns. If Trump and Epstein actually were close friends, it would be relatively simple for oppo research to uncover lots of stuff that wasn't in the Epstein files to indicate it.

In short, I suspect there's something in there that would prove enormously embarrassing to Trumpedo and peel away a large numbers of his supporters, well beyond their disappointment at there being "nothing interesting in them."

I think that's very improbable. What could it possibly be? They weren't close friends - and anything that actually implicated Trump in any kind of criminal activity would have been acted on long ago.