[Formendacil]

With regards to the Third Age possible survival of the Laiquendi/Nandor, it's not conclusive, but it is perhaps pertinent nonetheless that when Frodo meets Gildor Inglorion and his companions, he finds it a unique event that they are High Elves, suggesting that any other Elves he has encountered wandering around the Shire have not been (though Bilbo has met Gildor before, it seems this is Frodo's first encounter with High Elves--though not with Elves in general, if my impression is aright).

What this would implicate is that there are other "wandering companies"--since no Elves dwell in the Shire, and Frodo has never left the Shire's borders. If this is the case, and the others are not High Elven, then one must search for an alternative race. Here, it seems, the two main contenders would be the Grey Elves and the Green Elves.

Regarding the Grey, it seems entirely possible that the Sindar had wandering companies, just like Noldor under Gildor, but the Green Elves seem even ore likely on that count, especially insofar as my impression of First Age Eriador is that it was mostly inhabited, as far as Elves went, by Laiquendi who never quite followed Denethor into Ossiriand. Since the Green Elves never seem to have had a fixed abode in Eriador, they may always have been wanderers, and on that basis, it seems to me that if they had any descendants (as seems possible, given that even the ever-diminishing Noldor still have a wandering company or two), they would still be transient, like all their forefathers before them.

A case for plausibility, anyway, seems quite easy to make.