How much could one Bitcoin be worth?
In 2020, there will be ~18,375,000 BTC in circulation. $1,137,500,000,000 divided by 18,375,000 = $61,900 per coin, ~+2,200% from today.
How much could one Ether be worth?
This is a little harder to calculate due to the somewhat unknown supply of Ether in the future, how Proof-of-Stake might change new Ether issuance, and the impact that the Ice Age will have on time between new ETH issuance.
The original 2014 issuance model, stated a projection of ~162M ETH in circulation in 2020, however /u/manly_ pointed out that Vitalik has said it would be closer to 100M, so for our rough math we’ll use 100M ETH.
$1,137,500,000,000 divided by 100,000,000 = $11,375 per coin, ~+4,000% from today.