A few hours ago, iOS hacker MuscleNerd, announced on Twitter that an untethered iOS 4.3.1 jailbreak is on track for "Funday" release. Funday, or the trending twitter topic #sundayisfunday, is a related nickname for a jailbreak that got released over two years ago on Sunday.
A lot of unofficial and fake twitter jailbreak accounts are saying the untethered jailbreak is scheduled to release at 12:00 AM EST Monday, which is only a couple of hours away.
Both the Redsn0w (for Windows) and PwnageTool (for Mac) are scheduled to release in a few hours, jailbreaking all iDevices, except for the iPad 2. The latest iOS 4.3.1 jailbreak, when released, will be able to jailbreak iPhone 3GS, 4 (GSM), iPod touch 3G, 4G, iPad 1 and Apple TV 2G.
Recently, the iOS jailbreak community announced an unpatched flaw in OS 4.3, which would have meant a jailbreak tool would have been released sooner. However, Apple seemingly discovered the flaw on its own and issued a minor update to iOS 4.3.1, which blocked the vulnerability.
Update: PwnageTool has been updated and released for iOS 4.3.1 (Mac OS X). The windows based jailbreak tool Redsn0w is expected to released shortly.