So what happens next? This shows that we can run code via this exploit. It won't be too hard to develop an eLoader that can use this exploit on v2.0 - v2.6. v2.7+ will be harder, due to extra security, but will happen a little later. Kernel mode is unavailable on v2.8, but it is likely that a downgrader is possible on all other firmwares. But then, with the possibility of kernel homebrew running without the need for a game UMD, why would you need to downgrade?
http://www.psp-ita.com/upload/fileup/psp/Helloworld_all.zip
http://img179.imageshack.us/img179/5638/multifirmsh5.jpg