If the market were efficient, it would already price in the dilution from newly minted coins, as it does for share dilution in the stock market (which is actually quite common due to employee stock options). However, every indication is that the bitcoin market is not at all efficient. It is largely driven by speculators playing a greater fool game, not investors who are betting on intrinsic value per bitcoin based on a future estimate of coins outstanding. The result has been a series of manias and panics, which will continue until real buyers enter the market.