Yesterday pod2g reported that he is now working on porting his untether exploit to the iPhone 4S and the iPad 2 (devices with the A5 processor). He had some issues with the A5 caches, but after just one day of trying, it looks like the issue has been resolved.
OK, figured it out, the A5 cache is not a problem anymore.
I sorted it out by doing the untether in a single thread and by flushing all the dcache then all the icache in a row at a strategical point of the process.
It took me like a hundred of tests to find the key. Hard for the nerves.