They announced how worlds would be shuffled.

[Kurando]

Did we really think the status quo was going to stay though? I mean yeah it's understandable that players now have make choices, but adding new worlds to current NA centres wouldn't of made much difference in the grand scheme of thing, as it would of been the same Congested and Preferred worlds appearing in the update every day. Now adding new worlds (to EU) and also moving around current ones (NA) would have a bigger effect, but whether they will turn out as SE hope is a different story. Not completely behind the EU worlds being split though but having 12 worlds on one centre could be problematic...