Trion suddenly felt that their game Rift needed a lot more trial servers, and thus "encourages" the players to move from those 11 servers now designated as trial servers to other servers. Less charitable people call that a server merge, which is generally a sign of decreasing subscriber numbers.
I do believe that part of Rift's success was due to being a new game not totally different from World of Warcraft. And I do believe that Star Wars: The Old Republic is the current destination for people looking for a game that is new, but not totally different from World of Warcraft. Thus I would speculate that declining player numbers in Rift have a lot to do with SWTOR being released. What do you think?