I don't like this method of categorizing holiday skins, it'd be easier to keep the holiday skins limited like they've always been and start adding older skins to the legacy list over time. No one has complained about limited skins until now (unless they were sad about missing the limited sale of those skins or about additions/improvements to the skins).
It saddens people that they missed out but they move on. They won't when the 3rd year Snowdown skins could be available in the future (the feedback of this thread proves that). Let's be honest here, it's not fair to include 2011 Snowdown skins as legacy and the first 2 Snowdown year skins (or even the other holiday skins) as limited. Why shouldn't players have a 2nd possible chance to get their Silent Night Sona or Haunting Nocturne skin but have a possible chance at Snowmerdinger or Mistletoe Leblanc? However, if this is the path Riot wants to take with legacy skins, they should have a 24 hour final sale of the limited holiday skins or something to balance things out.
In any case, for the future, please just show the skins we can currently purchase from the store (with the exception of the skins that are coming out next patch). It just depresses me when I see "Unavailable" for a cool skin.