Decentralized exchanges are the way to go, but they will never deliver the same level of usability and convenience as the current centralized exchanges are doing ~ that's quite a big thing if you want to attract average joes.

Another major problem is that it is practically impossible to incorporate fiat into a decentralized exchange, but then without losing the decentralized aspect ~ current decentralized exchanges fail to deliver in that front.

You could say that a token-like system such as Tether may end up being a decent workaround 'solution', but Tether is based on how much USD sits in the reserve of a service, and thus can't be seen as decentralized.