I think it will take a while before they can become a real option for traders, and I'm not even talking about professional traders, or institutional investors. I'm actually talking about normal daily traders that need a fast platform in order to process a lot of orders daily. They are simply to slow, and if sometimes it's a nightmare just to sell some tokens, it would be nearly impossible to try to scalp the market.
For professional and institutional investors a lot of other issues come into place, like liquidity and security.

Decentralized exchanges have a great concept, but they need to evolve a lot, in order to stop being just a place for users to buy or simply dump some tokens.