Dynamic Range/Lattitude & Camera Development

Hello,

I am a 5DMKII & 7D user. These are very capable cameras and paired with nice lenses produce fine results.

I find resolution is not on my mind but I do wish I could have a camera that offered more dynamic range. It seems DSLRs have been at the 9 1/2 stop range for a while.

So I wanted to ask, is there a technical reason holding back the development of a 12 or 14 stop DSLR? Is this the most difficult thing to achieve in sensor development?

21MP is fine for me but it would be nice to retain more detail in the highlights & shadows.

Thanks for your input.