New sensor? New sensor? We don't need no stinkin' new sensor! We got Digic 6 coming!
Here is an excerpt from the SX270/280 press release:
"The HS System pairs the new DIGIC 6 processor with a 12.1 Megapixel high-sensitivity CMOS sensor to deliver exceptional images in
low light, with minimal blur and noise, as well as
wide dynamic range – perfect for capturing shadowy detail as the sun sets on holiday. Using the DIGIC 6 processor and HS System, users can enjoy shooting with
incredible ISO sensitivity, up to ISO 6400, with outstanding results."
Canon couldn't be thinking that the same old 18MP sensor will be just fine in the 70D and 7D mkII because of Digic6 ... could they?