Blizzard is offering the possibility to move characters to less crowded servers. How it works? From a specified server to another specified server. Right now only from Arthas to Nathrezim. With more announced servers in the future.
The FAQs explain more details:
Characters on the 10 realms with the highest populations are eligible to move to a low-population realm.
The fact that the move is one-way and only between selected servers will allow guilds to move without ending on different servers and the fact that the guild layer is just about a chat and a tabard will make the process rather easy. Still, I do not believe that this plan will have a relevant impact.
This while I keep playing on the test server (dinged lvl8 before the shutdown) and seeing it “ugly”: quest tracker broken, meeting stones broken, minor problems with the animations, “garbage” dots around the interface… And this only about what I was able to see with a brand new character, because the confirmed list of bug is long and the unconfirmed one simply endless.
No patch for a while.