According to a series of tweets by MuscleNerd, an updated redsn0w and PwnageTool will be released today, April 3rd. Note: The Dev-Team was vague on the exact release time; the jailbreak could be released anytime within the next few hours.
The jailbreak is untethered and will work on all 4.3.1 devices (including the AppleTV 2 on 4.3) except the iPad 2. Users can also run it over an existing sn0wbreeze jailbreak.
via @MuscleNerdredsn0w+PwnageTool using @i0n1c‘s 4.3.1 untether (except iPad2) are on track for Funday release (USA time)