From another post:
What if Ripple captures bitcoin's current market share? $2
What if Ripple captures the value of all high-friction International payments that are now occurring? $20 (You could add a multiplier to this for additional demand from people holding XRP to make or facilitate the payments in the future.)
What if Ripple captures the value of an increasing volume of International payments driven by the reduction in friction? Maybe $120. (Same point as above, you could justify a multiplier to this.)
What if the economy triples in size, the volume of International payments increases, Ripple captures all of that, and people also use Ripple for all kinds of other things because it either displaces bitcoin or equals in size a bitcoin that's many times its current size? And we also expand the economy to other planets that also use XRP? And ...
As for how likely these scenarios are though, who can say. Ripple equaling bitcoin's current market cap sometime in the near future doesn't seem any more outrageous to me now than the idea of a bitcoin selling for over $1,000 seemed to me in 2012.
These were David's predictions from 7 years ago. We've hit $2 without approaching Bitcoin's market cap. He also claimed that it will reach $10:
It's [create xPool] what I'm going to buy when XRP gets to $10