These are all hypothetical situations that are years away. How can I promise you anything about them? What if someone else owns the company by then? What if the web is entirely replaced by some new holographic platform and we switch to that before the end of the company? What good is it providing a guarantee if in some hypothetical scenarios it won't apply?
The company is profitable, things are going fine, it's economical to support C3 as long as anyone's paying for it, and I don't see any reason for any of that to change for years to come.
I'd add C3 projects are a zip file with a mix of JSON files and image files, all widely supported formats. So in the long term it's perfectly possible that other tools can still open and use C3 projects.