There's a few vents that are blocked with connectors (they are behind the blu-ray drive..), so hopefully they can work it better than they did with the PS3 Slim, especially as it's even thinner.
But I will be corrected if they manage to keep it cool and silent. I just don't expect it though.
You keep saying this, yet the majority will agree that the PS3 Slim is extremely quiet and ran cool. Hell, even the original PS3s were far quieter than 360s at the time.
Nobody else seems concerned that the PS4 is going to burst into flames or cause deafness.