Yes, Bitcoin is in a bubble. A bubble develops when people are buying something expecting the price to rise and that activity drives the price beyond what is justified by any rational valuation.
It's hard to tell how much Bitcoin is overvalued, drastically superior 2nd generation cryptos could also be undervalued, even severely undervalued. Either way, there's far too much risk holding Bitcoin, when either its price needs to correct downward, much of the rest of the market needs to correct upward, or both.