IIRC, they've got Lv0 access and are trying to reverse engineer their way to the private keys. Some say it's impossible, some say it's a matter of time, some say the people who actually know how to do it just aren't trying (the argument being that 3.55 CFW does everything, so why put the effort into 3.6X except to re-enable PSN piracy?).
Naturally half of that is just rumours or unconfirmed tweets. I don't pay much attention because other people will, and when it's close to a proper release then there'll be a hype fest and everybody will hear. Until then, I just enjoy my PS3 for what it can do (which is admittedly mostly everything except PSN).