I think SE is thinking of the comming months, past experiences have shown that MMO servers are the busiest after an expansion and after 8 weeks alot of players take a hiatus or quit which results in a high populated server turning into a mid-low populated server. Servers like Balmung or Ragnarok will always be full, because of their popularity, but not all servers share this fate.

I agree that SE should lock Omega and add a new server (assuming the other servers have high population), but I feel that SE is looking few months ahead and is willing to let players deal with long queue time, if this means the server will still have a decent population after few months.