Obviously this isn't the be-all/end-all in terms of information, but from just a limited time with a poll up (see poll at http://www.ffxivcore.com/topic/13160-what-server-will-you-play-on-poll-with-the-new-server-names/), there are a few things that are trending upwards.
1) Cornelia appears to be the unofficial EU server (though there are some reports that the JP have also earmarked this server for the unofficial JP server)
2) The 3 top servers so far are: Lindblum, Mysidia and Figaro, in that order.
3) FFXIV-Roleplayers.com appears to have chosen Lindblum as it's unofficial RP server, with either Mysidia or Besaid leading the charge for the "overflow" RP server (if Lindblum is full)
I encourage those of you that visit FFXIVCore to vote on the poll as to what server you'll be playing on to get a more accurate representation of server population.