SmartThings does not make money selling hubs. Their business model is based on mining data (also known as analytics) that can be monetized one way or another, if not today, then in the future. Therefore, it’s naive to believe that SmartThings will ever allow anybody to bypass the cloud and deprive them from their revenue stream.
If you’re a developer, there’re many other home automation platforms to play with, both open-source and commercial, that don’t rely on the cloud services.