Recent rumors show that Canon is developing a new 21MP sensor for new APS-C DSLRs. This 21MP sensor is for the rumored 7D Mark II.
Some new rumors about 70D:
The April 23, 2013 date is not for the EOS 70D. And 70D may also use this 21MP sensor.
The issue is mass production of the 21mp sensor has not been finalized. This is delaying any announcement for a new APS camera that would use the 21mp sensor. Canon would prefer to announce a camera and have availability within 30 days of that announcement. -CR