Quantum computers require both very specific configuration for each problem, and cryogenic cooling. Both of those issues mean there's no reason to suspect they will find more than use as a daughtercard any time soon. Memristors, on the other hand, could replace CPUs, RAM, SSDs, bulk storage, FPGAs with one consistent lattice, a totally unified memory architecture, and an economy of scale that I don't believe has ever existed before.

And that's BEFORE you do any of the exotic research of moving the computing elements around during operation. Just imagine if there was no memory hierarchy, where accessing a byte in mass storage is as fast and as easy as accessing a register. Quantum computers can't replace commodity hardware and there's no reason to think they will. Memristors, on the other hand, are one of the fundamental circuit elements and are destined to become as widespread as resistors, capacitors, and transistors.