Speaking as someone who owns more than a few bitcoins, there are still many threats that could drop the value to near 0 in a matter of hours.
1. An exploit or bug in bitcoind that either takes down the network or allows theft of coins.
2. Discovery of a weakness in the underlying cryptographic primitives, or their specific implementation in bitcoind.
3. A hack of several mining pools at once that allows a 51% attack.
4. A crippling hack of multiple of the main exchanges or wallets at once: Mt. Gox, BTCChina, Coinbase, and BitStamp.
5. Regulatory action threatening to outlaw or severely restrict bitcoin.
6. Real brute-force 51% attacks may still be possible by an attacker with access to cutting-edge semiconductor fabs and a very large budget.
I think it's clear by now that the general concept of digital currency has a bright future, but betting on bitcoin specifically is still a risky investment.