Question for DEV Servers in ARR?

[FedeMax]

So let's say SE gives the information next year in January that Sargatanas is going to be a EU server, when you log in it gives you a choice to move or to stay and that you will not be able to move again until 6 months later. How are you going to find out if the people you play with are moving to a different server or are going to be find been in a server that some of your friends are already gone and it gives you a worst lag and the JP server?

If all of the servers stay in Japan I would not have a problem with that, it is the lag of information since we are having regional servers that concernds me.