Re: 100 bitcoins. Will I be a millionaire by 2020?

I think btc will reach about $500 sustained price by 2020.

I think you're wrong by several orders of magnitude in one direction or the other. i.e. $50,000 or $5.

I agree with the latter post, although not necessarily 50K, could be 10K-50K or $5
Reason#1: $500 is way too little for serious transactions as market cap of ALL bitcoins would be less than 10bil (19.5-19.6 mil BTC in 2020 X $500).
Serious currencies are trading in trillions (total ~$5 trillion a day)
At 50K bitcoin will be ~950 bil, still not enough to support major currencies trading, but getting there.
Reason#2: i don't think that serious exchanges can survive on a single measly 10b asset price item. We have multiple exchanges being worked on.
If it fails, then $5 is much more likely than $500

1. See: velocity of money.*

2.There's definitely some suspect logic in "many exchanges being built, thus price must rise to support them."

*If the 2.7 tps screw-up ever gets patched, that is...

1. i don't see a contradiction because total US stock market value is 22 tril, US bond market 37 tril. These are large sinks of value, some small % of which might be represented by bitcoin eventually, hence not all bitcoin will be available to exchanges.
2. if you build it they will come...

Finally, I see a nonzero possibility of bitcoin failing. It's all or none scenario, and i don't see people investing significant % of their wealth in bitcoin, at least not yet.
My comment was re price being relatively stable and behaving like a stock. The main point is that it won't.