Nokia on Thursday sent invitations to bloggers and the press for an event at which it will unveil at least one next-generation Lumia smartphone. “You are warmly welcome to join us in London on 14 May for the next chapter of the Lumia story,” the invitation said. Specific details about the upcoming announcement were not provided. Nokia is reportedly working on a number of new Windows Phone handsets that will debut in 2013, including the Lumia 928 and a phablet with a screen that measures between 5 and 6 inches diagonally. An image of Nokia’s invitation follows below.