The server merge has been announced for a few weeks, but on Wenesday when they started the merges, there were some unexpected issues with the structure of data happened which have interrupted their schedule.
This issue caused there to be a risk, on some servers, under specific circumstances, of items having non-unique identifiers in the database. This in turn might have lead to some cases of player's items not surviving the merge. It didn't happen at all during our testing, and may have been a possibly rare occurrence.
Now the team is workinf hard on solving this problem. And resolving the conflicts in the database and fixing the problem with the allocation correctly to ensure it can't happen again and also ensure that player's items or characters are not risked.
merge process will almost certainly continue into January. Some additional ‘ground work' as it were to prepare the databases for the merges again. The community team will provide more details on this over the coming days and weeks in terms of schedules and when you can expect downtime so please keep your eyes out for details.