There might be a solution for the population bleeding.
Open a second lordaeron realm with x6 rates, RDF enabled and a less restricted marketplace.
Once the latest content is released merge the new realm with deathwing and ragnaros.
In the end we could have a hardcore x1 realm with around 10k population and a x6 realm with 10k population.
I wouldn't vote for opening another Lordaeron realm, especially if it were to have a higher rate and or a less restricted marketplace. Ragnaros and Deathwing have all 3 of those things (higher rates, less restricted marketplace and RDF) and both will get the Lordaeron core in due time so opening another realm like Lordaeron and merging it later will be like the server doing double the work to reach the same end.
At times Ragnaros and Deathwing both still have 3k+ population so they are still viable and necessary to house players. There is a low rate "hardcore", a medium rate and a high rate WotLK realm for players to choose from.
With Lordaeron currently at times having a "high queue" this can be appealing to new players ("WoW" that many players are trying to play on that realm, did anyone notice the joke? LoL).
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During the time waiting on queue to be up players can utilize a second account to play in the meantime instead of complaining about high queues and it doesn't involve anything extra to be implemented. If players want to sit and wait without playing at all it is their choice, not the server's/staff's fault that players aren't utilizing the options they have available in front of them.