When you loses wallet, it has the effect of removing money out of circulation. Lost bitcoins still remain in the block chain just like any other bitcoins. However, lost bitcoins remain dormant forever because there is no way for anybody to find the private key(s) that would allow them to be spent again. Because of the law of supply and demand, when fewer bitcoins are available, the ones that are left will be in higher demand and increase in value to compensate.
I think its less likely to happen. Many have already use this and with its technicality it would be probably recovered. I'm just so positive about it. Otherwise, other financial institutions may not be threatened with bitcoin. I believe people who had invested with this a lot will make ways to not let this happen. Nevertheless, we should always have a reserve money for our financial security. Bitcoin investment should only be part of our total assets. For the meantime that's its not yet lost, then we should have invested some also with other investments in stocks or insurance or having a business. Putting eggs in different baskets. Let's just be prepared for anything.