And I mean really, really lost.
A lot of people can't remember their passwords after 4 minutes since they set it up.
But apart this, there's several ways bitcoins can get lost, like in example if you have a wallet on a USB key and this breaks and you have no cold backup.
This will inevitably bring, in the future, to less than those 21 million cap.
And they WILL keep going down.
Is there a plan to reintegrate them?
I myself am responsible for atleast 5-10BTC out floating in wallets that are basically unrecoverable, some was just deleting the wallet or throwing out the old computer with BTC wallet that still had some on it (at the time a couple BTC was basically worthless and i didnt see any reason to keep it) another way i lost lil over 2BTC was when i bought some from ATM and had them sent to my phone wallet (which was not backed up) then the phone got left on side of highway while changing a tire since i used my phone for flashlight (those were actually worth keeping) but ya if just me 1 user of BTC has contributed that amount im sure the combined amounts of "lost" BTC will be high and are unrecoverable...