What could have been? I remember being so excited about this at that point, I was sure it was going to take a significant chunk of [famous web services still around]. They even send me stickers for Cap'n'proto..
With that done well, perhaps the next step would have been ready-made images. I could see it reducing friction for people if they'd rent a VPS, upload an ISO/IMG, and the resulting system was reliably secure. Then they'd use the Sandstorm interface to install apps with a web GUI.
There is still a roadmap documented here:
https://github.com/sandstorm-io/sandstorm/tree/master/roadma...