I agree that there appears to be room for both to coexist initially. Gradually though I think you will see the legacy servers wind down through attrition. Additionally I think you will see 30-70% of current PVE players insta-switch to new servers when they are launched. Why be third fiddle on a legacy server when you can use what you learned and be a big hitter on a new server? With those new players leaving, there will be far fewer up and coming players to trade with.