When 21 million is reached the bitcoin community might reach the conclusion that inflation is needed and invent InflationCoin.

Inflation is needed mainly because of these simple reasons:
1) a significant percentage of bitcoins will be lost because of crashed harddrives, lost passwords, lost wallets and so on... maybe 1-2% per year?
2) The human psychology likes growth - it is not a coincidence that central banks have a inflation target of 2%. That gives the population the illusion of a growing economy since your salary, your house and your stocks go up in price. People are happier in a low inflation economy than in a deflation economy. The small inflation will also inspire the population to invest their savings in an attempt to beat the inflation – that makes the economy grow.

So in conclusion bitcoin needs an inflation of 4% to adjust to a growing economy.

The main difference between InflationCoin and Federal Reserve fiat dollar is that InflationCoin cannot print more than 4% per year to bail-out banks, finance budget deficits, finance wars and so on...