I don't think there is place for speculation any way. I am expecting over time bitcoin shall be more stable to the point of total stagnation. Other currencies, well thats other kind of problem. There are more place for speculation there. Besides it is hard to tell what new powers shall try to get on bitcoin market. China tried  something, other countrys might try too. Maybe some country with less stable financial situation might try use more endure option for sudden changes of market. Hell, I wouldn't be surprised if people finally lose they confidence in dollar and might try something else. Investment in gold is dull and not always profitable. Even though with minimal risk gold and diamonds value always were artificial in some way.