GIt itself is decentralized, i.e. every copy of an repository is equal. It's easy to upload code to e.g. GitLab as long as at least one person has his own clone of repository.
Risks:
1. we might lose latest commits - not very probable, author of the commit would probably still have it in his own copy
2. we would lose all Pull requests - similar to regular commits, probably code would be available in author's own copy, comments would be lost
3. we would lose any CI/build automation - can be setup again on different infra but it's a manual step
4. we would lose wiki - not sure how up to date it is