The new iOS 4.0 final(X) has exactly the same baseband as iOS 4.0 GM, so it probably has the same vulnerabilities that can be used to make a decoding solution for everyone, and if this theory is correct, then the following is also correct: the same firmware = the same solution jailbreak that already exists for more than 2 weeks.
So all we have to do now is wait to see what MuscleNerd and the other approved members say, but at first glance everything seems identical to the GM version.