What specs have you read that say it's NOT the 70D sensor?
The main thing is that I haven't seen a single line of official specifications.
But going for inofficial specifications, we have seen claims to 1080p/60 while the 70D does 1080p/30. This could be just a result of the dual DIGIC 6 support, allowing more data to be processed. And we have seen claims of the 7D2 sensor being new. And we have seen claims of different ISO range. But we have not seen any of the claims saying "same".
So right now, the unofficial specifications have several hints at a change but no hints at the sensor being same - unless you take same form factor and same number of MP as meaning the same sensor.