I am playing on T3-M4, and from my point of view the number of 'looking for group' messages in the fleet chat have significantly decreased over the last months. I assume this is also true for overall server population. If a server feels dead, I imagine also more players leaving the game and only few migrating to other servers.
I don't see any reason not to merge at least the language specific PVE and PVP servers, since you now have both zones available on any server. Not sure about the RP servers - but is there really serious roleplay going on?
Personally I wouldn't even mind being put on a mixed language or english european server if it means actually more players online. Having to change my characters names would also not be an issue, i want to play this game with others not stare at my name tag all day long...
So yes - please start merging servers now!