It looks like Chpwn, planetbeing and Comex have done it again!
From twitter feeds of:
It appears that there is a working 4.0 userland jailbreak which just needs to be developed a bit more.
Although there has not been an official anouncement.
Remember; if you want this jailbreak, do not update to any upcoming fws as userland jbs can be blocked easily through updates by apple.
Fingers crossed that we will get a release soon.