The reason given is just that the Classic option was no longer financially viable, although players on Classic servers can expect nice welcome packages if they choose to hop to the Phoenix version of the game. No word on any cash shop closures or refunds, although those may simply transfer laterally. Our condolences go out to the players affected by this shutdown.
Echo of Soul, but it turns out that a lot has been happening with the game since then. The last time we talked about the game was when it was preparing for its Phoenix update, but since that happened it looks like the game has moved into having both its classic version and a Phoenix version. But not for much longer, as the game’s Classic servers are shutting down on May 23rd.
Source: Official Site