Bitcoin, Steem and many other currencies have a strong upside, and in fact have a long way to go before they level out. Of course, they've been experiencing strong growth, and that may be interpreted by some as being in a bubble.
But another view is that they have not yet reached their true value, and are in fact undervalued. That view seems to be more realistic.
Based on US national debt alone Bitcoin would be $1,000,000 each.