I am not familiar with IronKey, but I would think it would be possible to copy the (encrypted) contents of the hard drive an arbitrary number of times to allow for additional password guesses.
My understanding is that IronKey meets the FIPS 140-2
Level 3 standard, meaning it stores password hashes and keys in a tamper-resistant module physically separated from the memory component. If the key storage module is physically compromised, the self-destruct feature is engaged.
The standard was developed specifically to address the threat model you described. I think the potential security threats are still at the theoretical, academic stage.