This might sound a bit odd but the successor to the 7D might be this Canon 6D which features a 20-megapixel full frame sensor.
Though there’s no no final details on the specs of the Canon 6D, the biggest update to that line-up would be the full frame sensor which is now similar to the one on the 5D Mark 2/3 series.
The Canon 6D will also feature a built-in GPS, WiFi, Digic 5+ processor, 4.5fps, ISO range of 100-25600 (expandable to 50-102400) and full HD 1080p recording.
The 6D might sell upwards of $2,500 when it goes out of the market.
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No match with Nikon D600 in terms of features…