Switching Servers
They wont ever mix servers, would kind of defeat the purpose of WvWvW. Not to mention, with games like this having multiple servers is a hardware necessity. There are multiple reasons, just know that there really isnt a way around it.
Eventually switching servers will cost money (if it doesnt already) or you can buy gems using your own gold to switch servers. There are many people to play with on a server, and you should coordinate with any RL friends when it comes to choosing a server.