Apple today has released iOS 6.1 Beta 2 (Build 10B5105c) For iPhone, iPad And iPod Touch To Developers, if you're one of these developers and want to jailbreak it here is the guide for you:
Supported Devices Include
iPhone 4 CDMA
iPhone 4 GSM
iPhone 3GS (Untethered Jailbreak if old-bootrom)
iPod Touch 4G
RedSn0w 0.9.15b3 iOS 6.1 Beta 2 Jailbreak [Windows]
Step 1: The first thing you will need to do is download RedSn0w 0.9.15b3 for the Windows operating system using the download mirror below. You will also need to download the iOS 6 firmware for the device you are Jailbreaking, which can be found in the downloads section.
Download RedSn0w 0.9.15b3 (Windows)
Step 2: Once you have downloaded RedSn0w 0.9.15b3 you will need to extract it by right clicking on the zip file and then clicking the extract to folder option.
When RedSn0w has been extracted find the redsn0w.exe file, right click on it and click the Run as administrator option (if applicable).
Step 3: With RedSn0w up and running you will need to simply click the Extras button.
Step 4: Next click the Select IPSW button and select the applicable iOS 6 firmware file for your device. After RedSn0w successfully recognizes the firmware you will need to click the Back button, followed by the Jailbreak button.
Step 5: Once you click the Jailbreak button you will be presented a screen with preparation instructions for entering DFU mode. Read through these instructions, power off your iPhone or iPod Touch if you haven’t already, and then click the Next button.
Once you click the Next button you will need to execute the steps shown on-screen, which are:
Hold down Power (corner) button for 5 seconds.
Without releasing the Power button, also hold down the Home (bottom center) button along with the Power button for 10 seconds.
Without releasing the home button, stop holding down the power button for up to 15 seconds.
Step 6: After you have entered DFU mode, RedSn0w will begin processing the iOS 6 firmware.
When the firmware has been processed you will come to a screen with a few options for your Jailbreak. Ensure that the “Install Cydia” option is checked, and then click the Next button to begin the actual Jailbreaking process.
Step 7: RedSn0w will now begin jailbreaking your iPhone or iPod Touch. DO NOT interrupt or use the computer during this time. When the iOS device is finished being jailbroken it will reboot into a non-Jailbroken state (or in some cases will not make it past the Apple logo). This is because you have a tethered Jailbreak and will need to boot it using RedSn0w.
Step 8: Launch RedSn0w again if you exited out of it, click the Extras button, click the Select IPSW button, browse for your device’s iOS 6 firmware again and then click the Just Boot button. You will now need to put the iPhone or iPod Touch into DFU mode again. Once your iOS device is in DFU mode it will boot into a Jailbroken state.
Note: Remember that you will need to repeat Step 8 every time your iPhone or iPod Touch loses power.
This Jailbreak is only for developers because there is not reason why someone would want to update to the iOS 6.1 beta 2 firmware in the first place. The changes in the iOS 6.1 firmware are minute, and it is not worth risking the chance of missing the untethered iOS 6 Jailbreak.