Short answer: there is no proof either way.  

However, I don't think we are in a bubble. I think people are slowly clueing in to having a small part of their investment portfolio in bitcoin instead of or in addition to gold.  Bitcoin has limited coins like gold has limited mined weight. Bitcoin is drastically easier to transport and conceal then gold is. There is $8 trillion in gold holdings. Only $70 billion in bitcoin. As people figure this out in an exponential process (like flu spreading only slower) the relative market caps will close and bitcoin will be worth 100s of times what it is today. Hodl.