Do you really think we will be storing the whole chain for eternity? Isn't it quite optimistic that nodes will store the full chain? If we imagine a future with 1GB or 1 TB blocks.
We will definitely have some techniques in the future to skip full sync and still have the same security. If we don't store all blocks then it's not for eternity.
Only miners needs full nodes anyways, TB blocks would have have block rewards of 10 000 BCH at 1 sat/byte, 4 billion transactions per block, unlikely in the next decades.