User expectations are the main problem with USB-C. As long as people expect that USB-C ports are fast, computers will only have bandwidth for a handful of them, and USB-A will remain necessary.
In most applications, USB 2 is already fast enough. You can reasonably expect ~30 MB/s transfer speeds, which is comparable to a decent WiFi or a good internet connection. When a device needs a few more ports but it does not have the bandwidth for additional fast ports, the current answer is USB-A. It could also be USB-C, but that would require a way of telling people that not all USB-C ports are fast general-purpose ports.
I once heard an idea that established technologies tend to die in reverse order. The longer something has been around, the longer it will probably remain. I would not be surprised if USB-C died out before USB-A.