We have working decentralized bitcoin exchange already - Bitsquare, but so far we can't really say it is popular way to trade your bitcoins.
When you skim through an oderbook of Bitsquare you will realize that this exchange barely has any volume. Plus high fees for 'anonymous' trading are not helping either.
Because of high prices majority of traders will still choose centralized big exchange and subjugate themselves to KYC/AML policies.
Bitsquare is a decent alternative, but the only point of attention and also centralization, is that when you work with fiat from their supported services, the whole aspect of their decentralization goes to waste. The only thing that is really decentralized when trading on Bitsquare, is when you start coin to coin trading. Regarding their fees, they might be seen as steep, but I think at this point they are fair. Especially in case of you having no other option.