The only reason that bitcoin goes below 100$ is if the block chain itself is proven to be untrustworthy. It will then for sure go down to being worthless.
Even when bitcoin had its worse crash, it never went below 200 for long, if it even did at all. That crash had to do with a number of things, the major exchange turning insolvent, The Silk Road being raided, as well as numerous fake sell bots that were artificially driving up the price on mtGox. Still, the block chain remained trusted.
I don't even disagree that a major reason the price is so high right now is speculation. You probably think the actual price should be like 150(assuming you believe it has any value I guess), I think it should be closer to 850. But that doesn't change the fact that it is not selling for anywhere near those prices. The next time there is a new all time high I expected the whales to sell their shares off and crash the price, so they can then buy more cheaper and do it again after the panic selling.
But, if you see no value in the blockchain at all then you clearly have 100% faith in whoever controls the currency. I certainly do not trust the federal government as much as you.