Few hours ago, Limera1n was released to jailbreak all devices on iOS 4.1, although there's some bugs in the beta releases, it still working on new bootrom devices. So, to be able to jailbreak in the future using the same tools (i.e. on iOS 4.2 and newer), you have to save your SHSH blobs. You can follow those 3 steps to save your SHSH blobs of any iOS device.
Step 2: Launch TinyUmbrella and connect your iOS device to your PC / Mac. Now select ‘Advanced Option’. Your ECID number should already be there, and make sure ‘Location’ is set to ‘Cydia’
Step 3: Now just click on ‘Save My SHSH’ and wait a few seconds