I think with the way dPoS works it's almost impossible to continue on a legacy chain like that, which is why Steem endured 20+ hard forks without an actual chain split. Once you have that 17+ top witness consensus, now controlled by Justin Sun, any outliers running outdated versions will simply have blocks rejected from the chain. I believe Hive is less a fork in the truest sense, and more a new chain with the legacy open source Steem data imported.