They can, but then you're talking about a totally different physical scale of computer. Transistors are useful because we know how to shrink them to a scale of nanometers, in particular we know exactly how to do that with transistors printed with lasers onto silicon chips. We'd have to reboot the CPU manufacturing industry with new base materials/technologies.
It's hyper-specialized tech, so it'd probably take over a decade from now to be seen in useful, everyday technologies.
