Sia is a solid coin with a good roadmap. It has a very clear use case and it's easy to understand, compared to all the ICOs that are out there nowadays. There are a few things left to add to make it competitive with other centralized storage competitors like Google Drive. The devs are planning to work on them in 2018. It would be logical to jump in Sia now or somewhere in early 2018 before they release the mobile clients.