Exchange security has vastly improved since the early days and securing coins has become easier than ever before. So short of catastrophic 0-days and physical or social attacks I'm fairly positive that even centralized exchanges will remain rather untouched in 2018 (support issues and other problems aside).

Ironically the one exchange that got most recently hacked was a decentralized one -- Etherdelta -- albeit arguably it was the centralized component of it, namely their DNS.

In other words, from a security perspective decentralized exchanges also still have a lot to learn. While I love seeing decentralized exchanges hitting the scene keep in mind that they will come with their own sets of problems regarding both security and performance. We're likely to see a lot of issues and hacks with decentralized exchanges as well before they reach maturity -- either on the smart contract level, or caused by its surrounding infrastructure. Nothing comes easy, but it's a welcomed development. Due to the centralized nature of fiat I doubt we'll ever get fully rid of centralized exchanges though.