Sia development team decided to hard fork the network on October 31. After the hard fork, only miners using Obelisk miner which is developed by the Sia team will be able to mine on the blockchain
Sia team recently released Sia v1.3.6, which includes several important updates in addition to support for the October 31 hard fork. All the users who want to stay in the present Sia network need to upgrade before the fork. Those who reject the hard fork can continue to use the old blockchain code. If enough people rally around the old software, there could be a network split, and Sia could divide into two blockchains, in the same way that Ethereum split into Ethereum and Ethereum Classic, and in the same way that Bitcoin became Bitcoin and Bitcoin Cash.
Though many users are expecting a new coin from the hard fork but it will depend on the numbers of users that will reject the new code base.