I think it will be more than 19m that will be in circulation even while excluding Satoshi but I wouldn't assume it is lost forever, anything can happen, we are not the owner of the seed phrase neither are we in his/their mind.

While these said bitcoins tagged as being lost/dormant for too long, some of them are just not being access by the owners still waiting for a time when they may decide to move it, we saw things like happened this year. Also, some lost coins will also be found while a few will still lost theirs but as the value continue to increase the rate of losing bitcoins will be lower and the rate of even finding lost ones will increase well enough. It will become treasure hunt on the internet and the most valuable treasure will more likely be bitcoin.