Noone can proof that he is owner of the coins, if the keys are lost. So i guess, no. A “if 80years not moved, coins go to a community pool” rule is technically possible in a protocol. Yet i guess most holders would not want this.
Every cryptocurrency is just virtual. And you can devide the existing coins by any number you like. e.G. you can subdivide bitcoins further. Then create a name for the subdevided coin. In the first 40years we moved 1BTC. Now (40 years later) we move more 0,001 of a BTC. Lets give this amount a new name like 1 BTCS. Everything was virtual from the beginning. Why wouldnt people continue to use it? Apple stock is traded, even after the 2nd split of apple stocks. No problem.