I guess that I'm missing something, since imho we have the same now: any contributor can upload his local files and start a new git. ...Just the change history will be gone.
On the other hand... I was thinking on forks of git where we take advantage of blockchains and... surprise, I've found out that there are already such projects, like GitTorrent where "Git objects are retrieved via the BitTorrent protocol and references are stored in Bitcoin transactions"[1], or Git-Ssb (using Secure Scuttlebutt), or Mango "which combines Ethereum with IPFS or Swarm as a backend for Git"[1]
Maybe other options are also there and this can be a next step. However, considering rather unlikely the scenario Bitcoin git ever gets threatened by US govt, I expect the devs will just leave it on GitHub for convenience.
[1] The info and quotes are from this page, which is not mine, I've got it from a search engine: https://medium.com/@alexberegszaszi/mango-git-completely-decentralised-7aef8bcbcfe6