What precisely are you referring to? Do you want a marketplace where every single piece of information about a transaction is stored on a blockchain eternally or only where the bidding, purchase and administrative process is organized via a smart contract? I don't know how beneficial it is to produce blockchain-based transaction data for every single item that's being traded on a platform like Ebay or Amazon.
I'm referring to a marketplace where bidding, purchase, and administrative process is organized via a smart contract. Storing everything on the Blockchain would not be feasible because it would increase centralization in the long run. The main challenge would be dealing with scalability issues of the underlying blockchain network, as constant smart contract operations could "clog" up the network. I guess a high-performance smart contract platform like Binance Chain or EOS will be most suitable for a decentralized eBay or Amazon contender. At least, the idea is there. Making it a reality is another story. If something like this materializes in the future, traditional marketplace's dominance could decline as we speak. That is if decentralized alternatives become extremely popular in the mainstream world. Just my opinion
