Not that SE would explain every single Detail on their technical Plans to us, but i also think they would tell us if they plan to move the current existing server.
Speaking of deductive reasoning. Using Theories about Servers will be regional or segrated, without knowing if they are moving or not, is the same no? Why would you assume they would move in first place? But yeah, it is an assumption. Like it or not, assuming SE will move them is actually an assumption too, which is actually more expensive for the Company. So SE would need a good reason to do it.
Something i would like to add:
Most people obviously dont think about the cost of moving a Server. So why would SE move the Server, if they could save the Money and buy them in the Region of the Data-Center? It is not like a Game-Server is something you could carry around like a PC.
To give People an Idea. So it is more reasonable to let the current Server's stay in Japan instead of moving them, since the cost-factor would be hilarious to move the around the whole Globe. Like it or not, guessing around that SE would actually move them in first place is an assumption too. And also, since it would be expensive to do it, SE would need a really good reason to do it. Like it or not.