Birimbau on 22 February 2013
It's simple, according Yoshida, the console wasn't shown because its design is not finished, but he also said that its hardware is not finished either.
http://n4g.com/news/1178865/ps4-hardware-design-not-finalized-sony
So, I think the final hardware will be even better that the current one(we only know about memory so far).
