The issue is, the minute they open the paid transfers, all the half decent servers are gonna die.
Like sulfuras. Perfect server. You open or allow paid transfers, you can be sure its dead within the week. They gonna have to layer it. They cant offer free transfers off it, because if a big guild opts to move the waterfall effect will happen and you will end up with another incendius situation.
You also can be sure that already layered realms gonna suffer. Faerlina etc. They are already layered (and they should not be, and the devs claimed at the start of classic, they had the plan to remove layering as early as possible). If you add more ppl you will never be able to get rid of the layers, and all the transfer kids want on either the layered realms or the very high populated one short 500 ppl of being layered.
Its phase 5 and we still have layered realms and by opening up the locked servers (locked for transfer) the player base will just destroy these servers for good. If you want to play there roll a fresh toon. Either live with the realm you rolled your alt on or abandon it and start fresh on the server you want.
Nothing good will come of opening the locked realms.