Nokia started sending out press invites for a Symbian meet-up in London on April 12th a while ago now. People are speculating that there may be a big Symbian update coming up.
Nokia is moving to Windows Phone for its mobile devices, while Symbian will still continue to be active. Symbian was once the most used mobile operating system in the world for quite a long time, before Android came along and took its position.
Now, Nokia even contacted Engadget to say that this event is going to be a "media briefing". Probably because they know they need to do something with their operating system that is going down in the market as a platform.
Boy Genius Report predicts that "this could involve some hardware as well".