@Febo. 20 years, grin's inflation will be lower than 3%. The price will depend on adoption.
Price always depend on adoption. Adoption is part of a demand and demand pushes price up. Supply are the coins that people want to sell and is pushing price down. Newly mined coins or emission adds to the supply since a lot miners have to sell to pay their electricity. Influence of emission of a supply reduce over time.
However, Grin will need adoption more than most of the coins in the cryptospace that depend on deflation, moon math and pumps, I reckon hehehe.