You can make lots of theories, but honestly, the first people to find out are going to be the pirates. The freaking rich ones, look at the prices of Blu-Ray tech!

probably the game developer not yet 100% utilize the performance.

As it is with every console when it's first out to the market. The developers cannot use the console's 100% power right away, they need to learn it first and get some games on it.

Btw since it does have hard drive I would say that you can run linux on it! And I believe that the first OS to be installed by hackers would be linux. Think of xbox, I could run diabolic(live distro) and could install gentoo and debian(awesome that is?!) That's really not hard even if it's running on a totally new processor. What OS was run first on 64bit processors? Maybe it won't be long before we have a menu like

Please make your selection to run
1.Metal Gear Solid 4 (DISC)
2.Linux!!!!!!!

OMG!!! I get the chills right now guys... can't take it anymore, my mind will explode from excitement, if not my boss do it first.