Island Sanctuary as a housing solution ?

[Arielen]

What does completing 5.0 have to do with housing?

They're the only available population statistics that allow us to estimate the playerbase: we don't actually know how many people are actively subbed, let alone playing on each server. There aren't any stats for Second LT GC, lvl 50 and 2nd LT of a GC and lvl 50 offers us no hint at all of currently playing players. Per XIVCensus we know that there are 4,885,698 characters in total, 4+ million of which have likely quit the game, and only 647,345 of those are listed as active.

tldr we can only guess how many people are on every server based on what little info we have, since SE doesn't disclose the numbers