FWIW, services such as Blockstream Satellite exist. But it's not very popular and require you to setup it, so IMO it's not very viable alternative to internet connection.
If some real alternative for internet would ever be invented than I think bitcoin code would need to have hardfork and update.
I don't think hard fork is needed since Bitcoin protocol don't care what communication medium you use. What needed is to update communication logic of Bitcoin full node software.