If you're going to let the future determine your transaction patterns too much you will quite literally starve in the present. So even in that scenario there will be transactions and people will be happy to take your coin because they too hope that its value will go up. Obviously once a large fraction of world trade would be in a currency like that the currency itself would start to exhibit the same traits as the global economy and this effect would mostly cancel out any inherent properties.

Effectively: bitcoin was underpriced at the beginning to the point that it could only go up, the question is how far it will do that before it will have expanded to fill the niches where it fits. As soon as that has happened it will cease to increase.