I think a hard fork is likely in this situation. The result would be two different blockchains: Bitcoin Data (Bitcoin Core) and Bitcoin Money (Bitcoin Knots). Each of them would have a clearly defined role, keeping both of them relatively "pure". A lot of problems would arise from such a split, but it does make sense.

If we wanted everything to be located on a single blockchain, we would probably all end up on Ethereum PoW or something similar.