fordy on 20 February 2013
Sony wouldn't show the system or a release date because it's still in prototype stage at the moment. They even mentioned that at the conference. It was more of an effort to garner financial support form investors before manufacturing can begin.
To add to this, there is a LOT of skepticism behind cloud based gaming, particularly older games, because transmission between mediums via TCP/IP does not allow for superior latency times with controllers. Add extra latency for visual feedback and you have a potential disaster for games that require quick response. It's a similar reason why Duck Hunt will no longer work on LCD screens...
