Some interesting points in this article by Kaspersky:
https://blog.kaspersky.com/quantum-computers-and-the-end-of-security/2852/Earlier they made the point that encryption came about due to packet sniffing, being able to just grab the communication being transmitted as there is only a few channels one can use. But....:
"Quite amusingly, quantum physics might offer the remedy to threats it poses. Theoretically speaking, its impossible to eavesdrop on a connection if its based on a single micro-particles transmission quantum physics laws say that to try to measure one parameter of a micro-particle will alter another parameter. This phenomenon, known as the observer effect (and often confused with the uncertainty principle), should resolve the main issue of classical communications the possibility of eavesdropping. Each attempt to spy on a communication will alter the transmitted message.
In quantum communications, significant interference means that an unwanted third party monitors the connection. Of course, you want to prevent information leaks, as well as know that it happens. That is one of the reasons why modern quantum cryptosystems only use quantum communication channels to negotiate session encryption keys, which are used to encrypt information transmitted via traditional channels. So a potentially intercepted key is rejected and parties negotiate a new key until transmission comes unaltered. We see that quantum key distribution (QKD) system is being used exactly in the same role, as asymmetric cryptoalgorithms, which may fall to quantum attacks soon."
Of course, this doesn't affect hashing or encryption of stored data
The article ends this way:
"quantum devices will remain niche for many years, you wont encounter dozens of them in each office or apartment as it currently happens with Wi-Fi or smartphones. Thats why its too early to dismiss math classic cryptosystems, which are able to work over any physical communication channel, will remain in high demand for many decades. However, there is a need to pick new algorithms, more resistant to quantum computing."
So I think we'll have time and should take the time to choose the right encryption, etc... when the time comes, which isn't for quite some time. I also believe that it must be pretty easy to change out the algorithm without affecting anything else in the code. So in a lot of ways, worrying about quantum computers isn't required right now. Cryptonote projects, I would be concerned about, simply because their privacy could be completely unraveled, where as Dash is simple mixing, creating doubt as to who the funds originally belonged to and where they came from.
