What about the region between the red lines where cryptography breaks, and the grey zone where we are now? There may not be anything for quantum computers to do! There is some chance that there is a large "dead zone" where quantum computers remain completely unable to do anything new or interesting, before a sharp transition to new and exciting applications (such as breaking huge swaths of modern cryptography).

What should this chart tell you? Quantum engineers still have a lot of work to do, but they're making progress. When it comes to cryptography, Michele Mosca pointed out the main problem: Suppose quantum computers that can break RSA-2048 are 10 years away. If it will take 5 years for your organization to implement the new standards, and you need your secrets to remain safe for 8 years, then you’re already 3 years too late, since someone can record your encrypted data and break it later.

Now, maybe you think "cryptographically relevant quantum computers" are actually 15 years away, or maybe (like Signal, Cloudflare, Firefox, Chrome, iMessage, and many others) you have already transitioned to quantum-safe encryption, and now you only care about certificates and signatures, which don't suffer from the "harvest now, decrypt later" aspect of the attack described above. So you want to wait 5 years. This is quite risky, since the consequences of being wrong are severe. For this decision to be reasonable, you would need to be confident that quantum computing won't happen. You can scroll through earlier versions of this chart to see that progress keeps happening, and sometimes it jumps. While I'm still skeptical about fast progress, I don't think it's reasonable to be confidently skeptical anymore.