My best guess is 700 unique players on Era realms, maybe a bit more, as I mostly play allyside - I said so before All TBC servers will progress to WOTLK - #4 by Vanillataur-nethergarde-keep and I would not call this overestimating 
My best guess is 700 unique players on Era realms, maybe a bit more, as I mostly play allyside - I said so before All TBC servers will progress to WOTLK - #4 by Vanillataur-nethergarde-keep and I would not call this overestimating