It's not unusual for an MMO that the population drops after the opening rush of new accounts and enthusiasm. Some people will give up after the first 30 days included with their boxed copies. Others might last for another month or so before drifting away, usually back to another MMO they prefer (i.e. World of Warcraft). It's no surprise that most MMOs don't sustain the same number of servers that they have on their launch day. As the number of active players dips, it's better to condense your population onto fewer servers, encouraging more player interaction and reducing maintenance costs.
But sometimes the number of servers changes so dramatically that you have to wonder if something has gone drastically wrong. Yesterday, there were 56 Warhammer Online servers. Today there are 13. No matter how you spin it, closing nearly 80% of your servers can't be a good sign.
The good news, however, is that Warhammer Online is a game based on player vs. player conflict, which relies directly on population density. So if you were curious to try the game, there's no better time than now, with the remaining player base packed more tightly. There's also a free 10-day trial available, and lots of new content recently added.