In the coming days, there will be a pre-release of 1.5 coming out, and then, quite soon a release of 1.5. This will cause your Minecraft client to ask you to update. Please note that once you update, you will not anymore be able to connect to the server. In order to be still able to connect to the server, you will either have to cancel the update or then downgrade. It is highly recommended to use one of the free tools that allow you to run several versions of minecraft at the same time and switch between the current and the new version.
In order to allow players to use 1.5 features already, we will start a temporary server once the final version of 1.5 is out. This temp server will have no plugins at first, no protection, no lots and none of the money, goods or inventory that are on the main server. Whatever you do there will have to be hidden since we know that people will grief it. Connecting to this server will not affect in any way what is on the main server, everything there will stay as it is. Voting will add items to your deposit on the old server, and you will be able to retrieve those when you connect to the main server.
Once we upgrade, we will remove the current darklands and replace it with the world that was created on the temp server. So if you have anything on the current darklands, it will be deleted. Also, whatever inventory you had on the temp server will be deleted, too. Items in chests (but not ender chests) will remain on the world and become the new darklands. Same goes for the nether. The nether of the temp server will become the new nether on the upgraded server. Everything in the current nether will be deleted during the update.
I cannot say how long it will take to upgrade the current server to the 1.5 once it is released. We will have to wait for several plugins to be upgraded to deal with 1.5 features and that sometimes takes weeks. So please be patient.