Clarification: Sprout is zcashd 1.0.x, Overwinter is 1.1.x and Sapling is 2.0.x
The while these network upgrades are technically hard forks, there’s no sign of contention and an expectation for only 1 chain to persist. There is EOS halt functionality, a long testing period before hand for nodes and third-parties to take time with the upgrade and we have an ecosystem team who are diligently working with various third-parties to make sure everyone is on board.
For more info on the network upgrades and their expected outcome, this blog introducing Overwinter (aka Network Upgrade 0) is helpful: https://blog.z.cash/overwinter/
Edit: clarifying that EOS halt is “end-of-support halt” meaning, the user will be required to update to continue running.
The release schedule is also a good resource here: https://z.cash/support/schedule.html