I'm really excited to see where this goes in the community. There are some interesting projects using Firecracker such as Weave Ignite and firekube that I think could improve the security of Kubernetes. Also lightweight VMs are exciting in their own right.
They're almost sort of opposites? Firekube is the Kube control plane running on lightweight Firecracker-powered VMs. On the other hand, Kata Containers is a CRI runtime (like containerd or CRIO) that allows Kubernetes to schedule containers to start through Kata (which then allows the container to run via Firecracker or Qemu, IIUC). But also, I think in practice everyone uses Containerd/CRIO and then configure them to pass untrusted workloads onto Kata.
I'm not sure what to think of how all of this ended up.