coolghoul, I find it unlikely that any of the Quendi endured for that long, as according to even the most liberal reading of Tolkien's writings on the subject, they would have wasted away long before then. It implies that they (presumably Avari/Silvan elves) would've become something more akin to spirits, if that. If anything of them would survive into modern times, it would most likely be creatures not unlike the various Fae (fairies, elves, gnomes, trolls, etc.) of west European mythology. Or perhaps nature/tree spirits as exists in Pagan and Animist belief systems.
In other words, misty, spectral creatures seldom encountered by people deemed in complete command of their senses. Kind of like the Barrow Wights of their own time.
I really smiled when I read your comment - I strongly recommend that you try to read Shadowmarch. You might enjoy it.
The Shadows are a mysterious ancient race that now have retreated to the north. A mysterious 'Shadowline' separates the Qar (as they call themselves) from the humans. The Qar are living 'The Long Retreat' when one of their foremost warrior Yasammez ("The Scourge of the Shivering Plains" ) throws of the melancholy and decides that they will go down gloriously - other Qar who yearn to regain their mastery side with her. But even tho' the elderly blind Qar monarch has to permit this last attack, he has set other things in motion...
Later in book 2, some humans (unfortunate beings) cross the Shadowline - basically a mist or cloud - a living "breathing" thing and encounter what I think could be described as a misty, spectral, eerie, semi-alien world. There are creatures of flesh and blood but unlike any - they are all Qar. Some Qar are vaguely human, some cannot be recognized as anything but animals.
It's really good stuff!! Take a brief look at the Wikipedia entry
- the plot summary is vague enough to not spoil *anything* in the book.