The problem with Eldre'thalas is that the Silver Covenant high elves and the void elves are too hung up on getting Quel'thalas for either themselves or into the Alliance *with* the blood elves as per Vereesa, Umbric and Alleria's own words.
The Highvale high elves have their own self-sufficient village so wouldn't be interested either.
The majority of night elves see north-east Kalimdor as their homeland, rebuilding Eldre'thalas would be weird for them as it is far to the south, away from their homeland, and they made that mistake already with Feathermoon Stronghold.
The Draenei have shown no big interest in building a shared city, or nation, with the night elves except for one small village that probably got wrecked by the Horde during the Fourth War. There are draenei settlers with the Highvale elves, but again it seems neither of those two are interested in packing up shop and heading to Kalimdor.
That leaves the Shen'dralar and a very large group of those died during the Fourth War so alone they wouldn't stand a chance to reclaim Eldre'thalas for generations.
(ignoring Blizzard's style of writing in all this ofcourse).
Why, for the love of whatever diety, would the night elves, high elves, void elves and Highborne elves want to live in Arathi or Loch Modan?
That makes even less sense, especially considering that Forsaken evacuated there after and during the Fourth War, it is centrally located in Forsaken territory, large parts are held (in-Lore) by the Frostwolf Clan and it is a former human nation.
I support Alterac City as the new capital for the new Forsaken nation under Calia Menethil and Derek Proudmoore (until Capital City is cleansed and it's sewers filled up with concrete).
Precedent is there as the nation of Alterac was annexed by Lordaeron after the Second War and according to the war table the Forsaken evacuated civilians there during both the Battle of Lordaeron and during the Fourth War and the surrounding areas where heavily fought over during the Fourth War (and it's all about location too, Alterac is smack in the middle of core Forsaken territory with Stromgarde and Gilneas within "easy" reach incase of new hostilities).
No, they have their own thread and high elf fans have their own thread. It's better this way, trust me.