http://www.uesp.net/wiki/Lore:Falmer
Extensive discussion in the Lore Forum on the little fellas, ages before we knew TES:V would be in Skyrim:
http://www.gamesas.com/index.php?/topic/1054304-falmer/
The new setting presents an opportunity to address the fate of the Snow Elves once and for all - or to simply expand the lore. How would you like the lost race of mer to be handled in TES:V?
Personally, I think extremely rare and hard to find instances of Falmer would mesh best with the lore, and be the most interesting option, possibly with quests revolving around them to either reconcile them or wipe them out entirely. PGE 1st Edition on Skyrim, which I've been studying intently, says that runes and some artifacts remain - it would be intriguing to see and to harness powerful and ancient relics from the first wars between men and mer.