As far as I know, Polkadot is a multi-chain solution, which is just a way to connect multiple blockchains together to solve the scalability & interoperability problem between crypto assets on blockchains. Compared to Ethereum - the most developed blockchain platform in the world, Polkdot is more like a broker. In terms of transaction volume: ETH is $10.7B and DOT is $500M, so I still think that DOT will not be able to compete or threaten ETH in the near future.