According to what was said by a Microsoft executive during a round table Q&A at the Tokyo Game Show today, you can display your PS4 games on your Xbox One. Microsoft executive Albert Panello confirmed that Xbox One users could theoretically multi-task between both new next-generation consoles launching in November here in the United States and Europe.
"Any application can be snapped to a game... so if you wanted to be playing Ryse and Killzone at the same time, you could snap that," he said, as quoted by Gamespot.
This would be possible using the Xbox One's HDMI -in port. Panello's comments seem to indicate that this would also allow Xbox 360 and PS3 gameplay to be displayed on the new system as well.
Panello also warned journalistw that putting the Xbox One in a vertical position is not recommended or supported by Microsoft this time around. Both the Xbox 360 and PS3 supported this ability. The Xbox One needs to be firmly on the shelf this time around, it seems...