Things like how many enemies can it handle on the screen, complexity of the AI, and in general how much action will be going on. I suppose this won't be known until we see actual gameplay in action, along the lines of the Kid Icarus trailer but with gameplay of one continuous area in the game. --- ?
This happens with the reveal of new hardware every time. It's meant to showcase general presentation, not the console's absolute limits. That takes the shock and awe out of making the games in the first place. --- http://backloggery.com/davcube