We've been told multiple times that Cross-region data center travel is not a problem. The system was designed to allow it from the start.
It initially wasn't enabled because of fears about cultural differences. Now there are the concerns about player behavior (with respect to congregating on a single data center for PF) that has made them choose to delay it even longer.
Can't transfer or create a character if all worlds on the data center are Congested. Aether has already been there once and I have no doubt SE is prepared to do it again if necessary.