To be honest, I'm fairly skeptical of extreme and outlandish claims such as 1-million-dollar bitcoin.

At a cap of ~21 million bitcoins, for a single BTC to be worth $1,000,000, the entire market capitalization would have to be 21 trillion dollars. To put that number in perspective, that's roughly the size of all public US equities markets as of May 2017 as listed on the NYSE.

That is an insane number, and I think to see that level of growth in cryptocurrency would take nothing short of a full-scale societal revolution in the way we deal with money, IMO.

HOWEVER, that isn't to say that optimism is unwarranted. With the current rates of growth and mainstream adoption of cryptocurrencies, I still think that prices of $10,000 - $20,000 USD are realistic within the next few years