Today the old US board have been closed (everything is read-only now). Blue messages say that players should go to

http://us.battle.net/wow/en/forum/

if they want to post something.

When will this happen to the European forums (closure of this board and use http://eu.battle.net/wow/en/forum/) from then on?

We cannot yet provide you with an ETA on when this will happen on the EU forums, so the best we can give you right now is the good old Soonâ„¢ :-)