Not that much of a gamble. If the USG bans bitcoin, the FBI will have to destroy their private keys and that would be very bullish. It would still be traded here, just underground. An outright ban is very unlikely, even if regulation tightens to the point of scaring institutional investors and certain whales off. I think that is unlikely as well.
The US governement does not care about the FBI's bitcoins - it certainly would not take them into account when considering a ban on Bitcoin.
You say "not that much of a gamble", but how do you think the US government and TBTF banks will react when they inevitably come to the conclusion that Bitcoin is not something they can control? What happens when the IRS realises FATCA and other tax rules and collection policies are basically impotent when it comes to Bitcoin? Are you so sure they will sit back and do nothing?
A ban on Bitcoin in the US would be a tragedy, no doubt, but it would not necessarily surprise me. If the US acts, Europe will too. Russia, India and China are already half way there.
(For the record: still long Bitcoin, still holding some myself, still have BTC tied up in BTC denominated investments, etc)