Square Enix actually announced the service end of the Nintendo Wii version Dragon Quest X Online with the today released announcement.
According to it the Wii version Dragon Quest X Online will be playable until the Version 3 update and when the Version 4 release (scheduled to 2017 fall) you can’t login to the game anymore from the Wii.

So if you are a serious Dragon Quest X Online player but you are still playing from Wii you have to change the platform soon. Don’t worry, you can move your save and profile data file to the Windows PC, Nintendo Wii U and to the Nintendo 3DS version of the game.

You can read more about the Wii version service end in here: http://hiroba.dqx.jp/sc/topics/detail/49b8b4f95f02e055801da3b4f58e28b7/