Blockchain is present technology and will be for long time.
i read about Hashgraph it will replace Blockchain but need long time to do "must have new technology every 50 years"
Actually, atomic swaps are the beginnings of hashgraph being implemented. Perhaps the most advertised of the atomic swap technologies is the Lightning Network. Beware of the Lightning Network. It opens the way to CENTRALIZATION, and the banks taking over the blockchains, rather than allowing everything to remain in decentralization.
Right now most of the various "coins" have atomic swap activated within them, within their blockchains. All they need is outside programming to make it work. This programming is being implemented right now, and the result of major implementation will be hashgraph.
Hashgraph will ultimately be centralization for those who want it, and decentralization for those who don't, and every conceivable level of centralization/decentralization between the two. With hashgraph, people will have to decide how much centralization and how much privacy/freedom they want, and then act accordingly.
The next question to ask is, is there any benefit to centralization?
