Speaking strictly as an amateur who has studied epidemiology informally for a long time, old viruses tend to be less of a threat than new ones.
The reason for that is that we humans (like all other animals) are in a constant state of evolution with respect to our microbial foes.
Our immune systems stay one step ahead of bacteria and viruses by evolving defenses against them. Until they don’t. Then you get a major pandemic like the black plague or the 1918 influenza crisis.
But the thing is, if the microbes responsible for those pandemics were released in the world today, pretty much nothing would happened. Our shared genetic code already contains information to combat those microbes. We are descended from people who had some resistance to them.
It’s not impossible that some rare frozen microbes somewhere might be a real threat, but it isn’t very likely. The bigger worry is the constant dance of adaptation.
Microbes are always looking for an edge; they’re always evolving to find a way past our defenses.
The coronavirus is just one example of that process. This particular virus evolved a way to infect humans in just the right way to ensure its own propagation and survival.
We will eventually develop resistance to it like we do with flu viruses, or we will use technology to strangle its circulation and kill it.
But either way, investment in pharmaceutical companies is never a bad bet. ;-)