The retail counterpart is rumored to be released during mid to late June, however, recently we had a chance to check out PS3 Debug/TEST Firmware v2.40
Below is a video of it in action, displaying some of the new features. As expected, we can confirm from 2.40 onwards, the system software can be called any time during the gameplay. It appears the in-game XMB does not work while playing PS2 titles, probably the same with PS1 titles as well although we didn't have a PS1 game handy to try.
Anyway,enjoy the video!
http://uk.youtube.com/watch?v=WmVdPWD1hn0