Well... As someone outside of that arm of the industry, I have to wonder about what exposure there is to spectre, or what kind of patches are coming out for affected machines.
JunOS is based on FreeBSD, which doesn't have a fix yet. Not sure about the different variants of Cisco IOS. You wouldn't run untrusted code on a router though, so spectre would not be a concern. In fact, it's probably better not to patch for it given the performance degradation.