The DEX is coming.
There is some math, though this might be counting our chickens before they hatch.

According to https://coinmarketcap.com/exchanges/volume/24-hour/ , Top 10 exchanges' daily volume are above $10 million each.
Let trading fees be 0.1%: An exchange's revenue would be over $10,000/day or $4 million/year.

If Waves ranks with them, Waves hodlers will share this $4 million.
Suppose the interest rate is 4%. Waves Market Cap should be $100 million, i.e. $1 per WAVE.

And if Waves overwhelms Poloniex whose volume is around $200 million, guys, it's $20 per WAVE.