The math behind the Bitcoin is solid. However, since human and human interests are involved, the most effective threats are not directly against the math.
As I listed above: lazy software making and human conflict of interest could be deadly.
It is proven that bad code were written using public data as private key to generate public key (e.g. for an exchange wallet). By observing all transactions, a good analyst could get to a random wallet.
Similar threat is real to a hardware wallet, because the firmware is made by human, who can make similar mistakes (intentionally or otherwise).
E.g.If a hardware wallet generates 19 key pairs with the seed code correctly and ONLY generates the 20th based on the public key of the 19th key pair, there will be a great chance that a good analyst could get to the fund sent to the 20th key pair. Because both the private key and public key could show up randomly in the future in public. Zcash might be the answer for this threat.