Just had this response from Canon, they will NOT be updating firmware for the MG6150. :\ Not particularly impressed with that.
>>>>>Thank you for your e-mail and for contacting Canon.
Further to your enquiry about enabling AirPrint, this feature is not supported for the MG6150. There will not be a release of a firmware supporting this feature.
Unfortunately printing can only be done through the application, and as such e-mails and documents cannot be printed from the iPad or iPhone. This model is not an AirPrint printer (currently there are three, the PIXMA MG5350, MG6250, MG8250), which an iPad needs to be able to print e-mails or documents.
... This printer does not support AirPrint and will not be able to print e-mails or any other documents other than pictures.
Canon Services & Support