When this came up before, I actually wrote to the FBI (I think via the DOJ) to suggest that with the aid of an electronics engineer, they should be able to copy the data directly out of the unpowered phone, then they could break the encryption on the data without worry of it being erased.

I don't know how it's setup on an iPhone, but as far as I know typically data is stored on an encrypted filesystem residing on a memory chip. An electronics engineer should be able to work with that chip directly, bypassing the rest of the phone's electronics, and thus be able to copy the data and/or the entire filesystem to a more stable and accessible device. Then the encryption can be broken by brute force. It might take a while, but there's no worry of data loss due to exceeding some maximum number of attempts, because that safeguard is probably implemented in the phone's operating system, not the filesystem itself. Even if it is somehow integrated into the filesystem, all that needs to be done is load up another copy of the filesystem and pick up with the next decryption key.

Is the FBI really so ignorant?