One should always assume a vendor could vanish at any time, or your access to your data at the vendor. To assume this is a cheap mitigation against potential sadness.

At a minimum, you should be keeping hot copies of all contents of your repos currently hosted at Github, code, issues, etc. This could be in another svn system, or archive blobs in object storage you have full control over and can hydrate as needed into operating svn systems.

(risk management is my day gig)