According to this post at Blue's News, there will be price hikes in the EU on many World of Warcraft services. This kinda makes you wonder when similar price hikes will hit here in the US.
WoW Website outlines some price increases coming to World of Warcraft services in the EU on April 5th (thanks PC Gamer via Kxmode). They refer to this forum post for more details, saying the changes are "based on regional market conditions." The impacted services are all optional, and subscription prices will remain unchanged.