Leica Camera sent out invitations for an event in Berlin on May 10th, 2012:
"Leica celebrates the essentials of photography! We invite you to exclusively experience a whole range of product launches in a culturally and photographically unique atmosphere on 10-11 May 2012 in Berlin..."
I was expecting the M10 to be introduced at Photokina together with the new mirrorless camera system. Leica is very particular with their announcement dates - the M9 for example was announced on 09/09/09, so May 10th is a good indication for a new M10.