There are some incorrect assumptions in your post. Primarily the fact that the "size" of a coin doesn't grow as it gets transacted more. Old transactions are stored in blocks and it is not necessary to trace the entire history of a transaction to validate it. A transaction has inputs and outputs, where each input is in turn an output from a previous transaction. When a new transaction is received by a node, it will make sure that all inputs of the transaction correspond to valid outputs from previous transactions that haven't been spent yet. An output is considered valid if it's included in the current blockchain.
No more history is checked other than the last step preceding the new transaction. So the size of a transaction will not increase in the coming years and processing it will still be doable by consumer nodes on basic hardware.
Okay! Thanks for explanation! Now, I understand better. So, this increasing size of blockchain is due to increase number of transctions and blocks. Not increased amount of data hiding within
Hash/256 bit digest in bitcoin. Sorry! If I said anything wrong, I'm not a coder. I'm just trting to understand things in better way.