Here is the "official" reply from the dev team in regards to 3.0 on jailbreaking and yellowsnow.
Apple just released the fifth beta of their 3.0 OS. Back when 2.0 was still in beta, they released about nine beta firmwares, so it’s reasonable to assume we’re about half way through the 3.0 beta process.
As should be expected, the modern devteam jailbreak process is still valid. The picture below is 3.0beta5 jailbroken on an iPhone 3G. As we’ve said in previous posts, nothing other than a hardware respin can prevent our jailbreak from working on all exisiting iPhone and iPod Touches. They’ve chased our jailbreak so far down in the chain of trust, the only way they can fix it is in hardware.
jailbroken 3.0beta5
Because there are so many beta releases, we couldn’t possible refine, test, and release both PwnageTool and QuickPwn for each of them. That’s why we’re waiting until the final release.
But this is a good time to remind everyone. If you care about the yellowsn0w unlock, don’t go anywhere near the beta releases. You will lose your unlock, possibly forever.
So... once the final version of 3.0 is released they will release the "official" PwnageTool and you will then be able to upgrade to 3.0 without updating the baseband. It usually takes them 24-48 hours to get the release finalized.
PwnageTool is what you will need to use in order to update to 3.0. QuickPwn will not work for people that still need to use yellowsnow.