people generally underestimate exponential functions.
conservatively, in 2036 we will have 6 more halvings, therefore reward would be 1/32 of today's. Add to it the increased difficulty and , depending on exact numbers, you would need approximately 32X1.81X20=1158X price increase just to maintain network as is. Factor 1.81x comes from just 2% difficulty increase per adjustment period (12 days). 20 is the number of years.

629X1158=728K/bitcoin in 2036

It will be either something like this or network transforms into something else entirely or withers.
So far the price was pretty much at the edge of miners overall profitability (plus/minus), which is what is expected for a commodity. I don't see why this would change, bubbles and busts notwithstanding. therefore, long term prediction like this makes a bit more sense, in my opinion.

EDIT: I have one interesting example of the exponential function...you are in a spaceship that just left Earth orbit. You give an order to start accelerating the ship at just 1g (earth gravity) to make everyone on board comfortable. You have fuel supply (advanced type) that can last for many many years. How long would it take for your ship to reach speed close to the speed of light (c)?
Hint...the answer is quite astonishing if you run the numbers.