Why not?
I know the answer why not, because USD didn't kick off hyperinflation yet, but it's not impossible to see that happening in next few years.
Maybe you should also consider posts from Hal Finney who was making even higher bitcoin price predictions.
I came up with an even more extravagant estimate of $10 million a couple years ago on the cryptography list
Bitcoin has the potential to become the dominant currency for large-scale electronic transactions worldwide. If this happens, bitcoins could be worth millions of dollars each.