As far as I know, there are no truly decentralized exchanges so far that would mimic or replicate all or at least some of the features that an advanced centralized exchange (for example, Bitfinex) enjoys. It is possible to design them, but building a decentralized exchange would not be rewarding as its developers wouldn't be able to profit by it as the very nature of such an exchange assumes the absence of a third party. But if there is no third party, there is no way to receive royalties. Apart from that, it requires a coordinated effort from the developing teams of every major coin out there but that's very unlikely. We don't even see a lot of agreement even between Bitcoin developers, not speaking of others.