It always depends, it is always a bubble and it is not at the same time. First of all we need to understand a great difference beetwen tulips and bitcoin. Tulips are assets which holds aesthetic value and bitcoin is not an asset it's currency. It makes a huge difference! Because currency has got value as long as people belive it's got value. If opportunities of trading goods in bitcoin increases the currency value increases.
Example: In it's first usage bitcoin was currency for black market so it holds capitalization of blackmarket.
If particular section of white market will start to use it it's value will increase to this market cap.
Example: Assume people on NYSE will only trade in bitcoin it's value will increase by the NYSE capitalization so by $20,245 bilions.
Of course to whis cap with got to add bitcoin investment value connected to people who are not trading but holds currency for profit but this value is incalculable.
Summarizing:
Price of bitcoin is a bubble in certain amount of time and in the other certain is not it estimation when is extremely hard to do and almost impossible.
I will write a more detailed post about it.