Unfortunately the downtime is region-wide, as the transfer of data between servers requires the whole region to be brought down because of the variety of region-wide systems in the game. Unfortunately since Europe Central is the largest region, it will likely take the longest to complete these merges. We’re hopeful that this 16 hours will be a max, and if that’s the case we’ll bring regions up as soon as each of them are ready (and if it’s not, we’ll let you know as soon as possible).