It is true that the Bitcoin price has increased more than the investor’s expectations. With mainstream media covering Bitcoin, many people are jumping the lines to buy Bitcoins. Also there are some exchanges, from where the people are not able to withdraw their profits in USD.
These issues points to an upcoming Bitcoin bubble.
On the other hand major investment institutions have not yet started investing cryptocurrencies, so I believe we might be still away from a major bubble burst.
We would experience little pops along the way.
What happened during the Internet Bubble Burst?
When the internet bubble burst in the US, the major reason was that even the VC funding dried out.
In case of cryptocurrency, it is being funded by the public money and it is not going to dry anytime soon. If US stops investing, Russia might start investing or China might start investing even more. So according to my belief in the public money and the technology, no the bubble ain't bursting anytime soon.
Still you never know what may happen tomorrow. :P
Edit: I loved a comment written below and hence including the exact words in the post by 
"I'm not sure the comparison to any bubble that has been before is of any value. Bitcoin is different to tech and internet because it defines money itself. Thats a massively more radical idea than the already radical idea of free information exchange that the internet offers. Its truly unique point in history in my opinion.
As for the reasons why it isn't a bubble: it is always reaching out to new markets and infrastructure and engaging new tech innovations - generically speaking this is blockchain but really it offers a whole new world of doing things."
Mentioning another comment i really liked by 
"It seems that every altcoin has its difficulties to scaling up, mostly the solution is POS. But it is hard to control the speed of the inflation in POS, so lastly a new altcoin will come to the market for alleviating the problem. It is just a vicious cycle...."
