Only Dark Alex made true custom firmware from the ground up for the psp, and it was a lot of really hard work. Have you noticed custom firmware 6.xx since Alex retired from scene. No? well thats cuz he had reversed engineered and then recompiled lots code, and no one else wants that kind of pressure.
To always be depended on for constant fixes and updates, getting blamed for people bricking there consoles, and possible legal threats. Yes its possible for custom firmware on ps3, but we will be stuck on "3.xx" kernel for a long time as it takes a lot of work, the right hardware (EX: eeprom reader/writer, memory dumper, and good programmers/testers to prevent problems).
Not to mention the fact we can't yet modify and pack digitally signed custom .PUP files. MY guess is august, 2011 is a more realistic time frame for the PS3 to finally open "Pandoras Box" if You get my hint. Be patient and Keep your ears open.
PSP-3000 stopped pandoras battery and MMs exploit that could revive semi bricked consoles.Now its only partially hacked. PSP go continues this legacy being only semi hacked. As for PS3, I think $ony will do whatever it takes to increase profit and increase stock holders shares. This Means New hardware revisions and new Kernel to go along with it.
Alas $ony even removed otherOS and added a lot of New DRM in the 3.XX kernel. So much for $ony's policy of a partially Open platform. "Hen" is and always will be encouraged! Partial customization of the XMB is already possible but it wont be fully "pandora" for a long time yet.