I'll put this here without getting into specifics because I don't want to get anyone in trouble. I'm also not a developer, so most of what he talks about goes over my head, so it's better for me to keep to the basics.
I have an IRC buddy (I've known him for around a decade) that has worked for the same development studio for going on probably 4 years. Based on what he's seen, the potential for the PS4 to be substantially more powerful is there, but there's a lot of stuff the system is capable of that's not currently in the SDK, and won't be until sometime next year, probably summer or later of next year even. We will definitely see a ramp up of the system's potential over time, as we always do with game consoles, because the silicon is new enough that the software built to access it still needs to catch up.
When Cerny talked about a "super powered PC", he's not making that up, and the fact that you don't have the bulky OS and bloated drivers limiting resources like on a PC (this is not a new thing, Carmack has mentioned the inherent issues developing games on even the most beefed up PC, it's always the operating system and drivers holding back performance) means as the tool sets mature, we'll see pretty substantial jumps in games.
He also said similar things about the XB1. Clearly, on paper, it's not as powerful as the PS4, but is does have a lot of specialized processors that help to offload processes from the CPU/GPU, as well as the augmented ESRAM boost to the DDR3 in the system. The problem is, the more specialized chips you have in the system, the more work developers have to do to utilize those additional processors. If these are accounted for in the SDK itself, that takes some of the additional work off of the developer, but as of around a month ago, he said the XB1's SDK is still a little rough, while Sony's PS4 toolset is launch finalized and games using it right now can be certified for launch day if they're complete. That doesn't really mean anything for either system though, since tool sets will never be "final" final really until the next-next generation of consoles has been out for awhile.
He's said in probably 3+ years, the gap between the 2 systems could become more noticeable, but for now, they're both very capable of putting out what they need to and showing a substantial jump over current gen systems. He's excited for both systems, because they both represent a substantial ease in development than the current generation has on both sides.
Like I said, a lot of basic information. He did say their emphasis based on requests from MS and Sony is 1080p with a minimum of 30fps locked if at all possible. That will likely shift to 60fps for a lot of games in late 2014/early 2015 on at least one system. That doesn't mean every game is going to be 1080p, it just means that's what MS and Sony would both like to see for obvious reasons.