As you can see in the image above Sony and Nikon Listed as Medium/Large Format Exhibitor at PDN PhotoPlus Expo show (Oct 23-26) Exhibitor details page, We are the first website to the publish Nikon Medium Format Lens patent information few days ago (see here) and we truly believe that Sony is also fully capable of making medium format camera / sensor without any doubt.
+1 Canon is not listed as Medium/Large Format Exhibitor.
So it may be possible that we may see some prototypes of Medium format camera from Sony and Nikon at PDN PhotoPlus Expo show (Oct 23-26), however it is confirmed that Sony will announce Sony NEX-FF, NEX-7 successor, A5000 on October 16.
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