I thought the same thing when i was watching it at the PS4 reveal. I was debating if it was real or if they just added that at the bottom to make it look like it was real  gameplay.

Yes, companies often do that at the start of a gen, to give people an idea of what their vision is. Final Fantasy XIII's fist "gameplay" video comes to mind... 

But there is any confirmation or evidence? Like the Killzone 2 demo in E3 2005 (in any case the final game was close to the demo).

No, there's currently no evidence. All we have are Ono's words. So you are free to believe him or not. Until we see footage running live from an actual PS4...

I think you'll choose to believe him, since you seem to overhype the PS4 quite a bit. =P

Why I will doubt the words of somebody else without prof or evidences?

Deep Down is ingame... there are jaggies... It can be running in a PC but it is real-time for sure.

This video evidence the Demo is real-time...

http://www.gametrailers.com/videos/1bajnx/deep-down--working-title--pop-block--debut-trailer

That looks pretty good but lacks the post processing of the PC version. If people honestly believe that this represents the pinnacle of the PS4s abilities then you are very much mistaken.

stop making excuse and you are no postion to be calling anyone fanboy

this trailer was more then likely made not knowing the full specs of the PS4, I doubt it'll have much of a problem being on par as PC.

Sorry but did I lost anything?

Reported.