My guess is that about 1 million are permanently lost.
So, as time progresses, more people lose BTC forever, there will be less BTC in circulation and they will become more valuable as there are fewer.
At the rate they are being lost, in twenty to thirty years there will be very few BTC in circulation.
Does that not beg the question about security of wallets. How can wallets become 100% secure?
It is hard to imagine that permanent loss due to untimely deaths, forgotten passwords, paper with private keys being misplaced (or lost when a house burns down), etc. can account for the degree of permanent loss that both of you estimate.
Keep in mind that it is probable that most stolen bitcoins do not fall into this category (some of the the thieves may be ideologically motivated people who want to simply steal coins in an effort to weaken the system, but I suspect that the overwhelming majority of thieves intend to spend what they steal).
