Bitcoin was created in 2009, it was created to be used as a currency. As I have already written about currencies and what exactly it means for bitcoin to be a currency I shall not digress.
However once understanding what it means for bitcoin to be a currency you then understand that the reason Bitcoin holds its value is only if it is used as a currency. If bitcoin is not used as a currency then it really does become a 'bubble' That is to say that at 10,000usd a bitcoin if it has no use as a currency is 10,000usd overvalued.
What makes that 10,000usd valuation accurate is only if bitcoin is used as a medium of exchange. Once you understand this you can begin to speculate with fair accuracy as to what bitcoins natural value should be and what stabilizes its trading price.
Thanks to the invention of TOR in 2011 The Silk Road was created: this trading black-market platform primarily used Bitcoins as the medium of exchange. Due to its illegal nature, using conventional currencys which could be traced by the police, was simply not an option. So the criminal underworld had an alternative, that is Bitcoin.
Since then the dark-net has been using Bitcoin primarily, (although Monero is also widely accepted). That is now almost 8 years ago, This gives Bitcoin as a currency huge stability. Even now on the darknet Bitcoin is the most used currency. That means that no matter what the trading price is; it is continually used as a medium of exchange over the net.
Furthermore now that Japan itself has adopted bitcoin in many stores, Microsoft and steam are other companies to accept it too now. This adds HUGE stability to bitcoin, this stability is not shared yet with other cryptocurrencies. Adding on to this that bitcoin is capped to 21million units which makes it hold its worth just like gold does (its a finite resource), bitcoin seems not just to be stable already, but just streets ahead of other cryptocurrencies in its stability. So much so that 10,000usd or thereabouts is not a 'Bubble' at all.
I would argue that other cryptocurrencies are benefiting from a Bubble however this is purely because you can not really use them to buy much as of yet.
I certainly recommend investing in Bitcoins, due to the fact you can actually buy a large number of products already with them. I hope this continues to grow and so long as it does grow the price of a bitcoin will surely go up.