I started writing this post thinking that I agree with ascent but couldn't articulate the agreement.
Then I imagined the world where a car costs 0.00000001BTC. Then I imagined a news report that 10 BTC has been discovered by someone finding an old wallet.dat on grandpa's old computer. What would a discovery like that mean when all the bitcoins have been minted and the market has adjusted to the limited supply (including the lost coins)? Most likely that would result in inflation. As the supply of bitcoins increases, the prices will rise. We'll be where we are now with USD and other currencies. As coins get lost the system will have to adjust because there will be not enough coins to go around. As coins get more expensive, the hoarders will release them into the system, thus stabilising the price.
What ascent seems to object to the most is the fact that nobody knows how much currency is available. Everyone knows that there's no more than 21M, but no exact numbers. Supposedly, this leads people to be uncertain about the currency. As long as the algorithm is strong and new money cannot appear from nowhere, there's no uncertainty. Just because you know that I have 1K BTC, doesn't mean you can be certain how I will use it to take advantage of the market. When the story unfolds in such a way that earning 0.01 BTC per year is enough for you, the fact that I gained 10BTC will have no radical immediate effect on you. I'll just be able to employ 1000 of you which would keep you feeling happy. There will not be an overall uncertainty, just like not everyone thinks that there will be a war tomorrow.
When 10BTC is enough to employ 1000 people for a year, I believe I will take all the necessary steps to make sure I, or my descendants, do not lose the funds. Any coins lost today, will have such a big bounty on them in the far future, that it may be the biggest driver of innovation in cryptography with an aim to recover lost/inactive coins. Inactive wallets that are not kept up-to-date with technology will be more easy to compromise and the BTC will enter the circulation again.
I know there are wallets being lost today and I'm not uncertain about BTC. I think BTC is still good.