iPhone Dev Team’s Member, @musclenerd had earlier pinched the holders of A4 Devices which are iPhone 4, iPad ,and iPod Touch 4G. He stated that they will be able to jailbreak any firmware in future for iPhone 4, iPod Touch 4G, and iPad. It has become possible by embedding Limera1n exploit along with @comex’s hacks into PwnageTool.
You will actually be able to jailbreak iPhone 4, iPod Touch 4G, and iPad using custom firmware cooked by PwnageTool. The upcoming iOS release is 4.2 and we can be assure that iPhone 4, iPad, and iPod Touch 4G on 4.2 firmware will be jailbroken within some time after release. Earlier, iPhone Dev Team has started the cycle by releasing PwnageTool 4.1. It is expected that they will soon reveal more information regarding the ability to jailbreak any future firmware on A4 devices.
iOS 4.2 is specially a gigantic upgrade for iPad owners as it will bring multitasking and many other features which are being enjoyed by iPhone and iPod Touch users since iOS4. The possibility to jailbreak iOS 4.2 on iPad within no time is very exciting after the official release. Also, it looks like we will also be able to jailbreak iPhone 4 4.2 and unlock it.
Update 8: Sn0wbreeze will likely support tethered iOS 4.2 jailbreak for OTB device.
Update 7: Cydia Update will be pushed after iOS 4.2 is revealed in public.
Update 6: iPhone Dev Team asks to prepare for iOS 4.2 Jailbreak and Unlock.
Update 5: Cydia is saving SHSH Blobs of iOS 4.2 Beta for untethered jailbreak.
Update 4: Early untethered 4.2 jailbreak will be a treat for those who have saved SHSH Blobs. [How TO]
Update 3: Apple release iOS 4.2 GM Candidate and you can jailbreak 4.2 GM on iPhone 4/3GS/3G, iPod Touch 4G/3G/2G, and iPad
Update 2: You can get the guide How To Jailbreak iOS 4.2 Beta 3 on iPhone and iPod Touch.
Update 1: iPad 4.2 Jailbreak has been achieved by ih8sn0w.
Jailbreak Guides and Tools:
Jailbreak iPhone 3GS 4.2 | Jailbreak iPhone 3G 4.2 | Jailbreak iPod Touch 4.2 | iOS 4.2 Jailbreak | iPhone 4.2 Unlock
Download Limera1n | Jailbreak iPhone 4 4.1 | Jailbreak iPad 3.2.2 | Jailbreak iPod Touch 4G | Jailbreak iPhone 3GS 4.1
Download Greenpois0n | iOS 4.1 Jailbreak | Jailbreak Apple TV 2G

