Apple released the iOS 4.0.1 download today to resolve the reception issues iPhone 4G users were having. In case you're wondering, yes it's possible to do a iPhone 4.1 jailbreak.
Although you can jailbreak iPhone 4.1, you should hold off on updating to iOS 4.1. In fact don't even update to iOS 4.0.1 yet, because it's just a small update. Apple will be releasing an iOS 4.1 download (no ETA on that) which will be a bigger update, so I recommend waiting for that. It's also important to note that if you want to unlock iOS 4.0.1 don't update until we know the iOS 4.0.1 update doesn't block the unlock.
The best way to stay up to date with the latest jailbreak iOS 4.0.1 information is to follow @QuickPWN on Twitter. Maybe we may see a iOS 4.0.1 jailbreak from the following:
- iPhone 4.1 jailbreak with redsn0w - redsn0w is no doubt THE best jailbreak out there. It's created by the famous Dev Team who makes reliable jailbreaks. It will definitely be updated to support iOS 4.1
- iPhone 4.1 jailbreak with Spirit - Spirit is the easiest jailbreak out here. It's created by comex. There may be a Spirit Jailbreak for iOS 4.1, but don't count on it as Apple could easily patch that.
- iPhone 4.1 jailbreak with limera1n - Geohot was going to release a limera1n jailbreak for iOS 4.1, but it looks like he has left the jailbreak scene for now. He did state that someone else may take on his work before he closed his blog and Twitter account.
Update: You can jailbreak iOS 4.1 beta using the redsn0w 0.9.5 beta 5 software (thanks to Dev Team). Download it for Mac here, or Windows here. Don't know what this is? Stay away then, I recommend waiting for the iOS 4.1 jailbreak.