This is actually a very interesting question.

When bitcoins are lost to a wallet and put out of circulation, they're basically becoming a kind of "burned token". ICOs burn tokens to raise the value of every remaining token. If say they have $1mm investment on 1mm tokens then there would be a dollar parity. However, if when the money is raised the company decides they want to burn 500k tokens then each token would double in value. There would now be 500k tokens each worth $2.

Fiat currency does the complete opposite, as they print more money and devaluate the value of each note. There are other factors to consider though, like the demand for bitcoins and the overall state of the market. For the purposes of answering your question, however, lost coins would limit the supply of bitcoins making their value increase. Some people predict a single coin could be worth $250k, others (John McAfee) predict $1mm/coin in two years time. Who's right? We'll have to wait and see.