It's not a sequel, neither is it pronounced "cubed" so what exactly that superscript 3 is doing on the end of this RPG/block-em-up hybrid is anyone's guess. What I can tell you is the absolutely gorgeous Planets3 is currently chilling out on Kickstarter with a few days (and thousands of dollars) to go. It caught my eye for two reasons: a creative element that allows for more customisation - wheels, triangles, and so on - and an integrated story/adventure that helps to direct the action. While I'm often enamoured with the idea of being totally free to build, explore and create as I like, actually doing it usually bores me after a few hours. A pre-planned mystery to solve, procedurally included in the world, helps to keep me interested. Have a look at their trailer and some thoughts on a very early Alpha build once you've mined through the crust below.
What I played wasn't so much a game as an engine demo. There was no crafting to be done and while blocks could be mined out, there wasn't any reason to do so other than to see what was below. What it did allow me to do was fly around the world and out into space, to observe the procedurally generated landscapes. In a word, it's beautiful. Rather than lowering the rendering detail of the whole, a distance at which every block stops being drawn and is merged can be set. While this creates a certain amount of pop-in when surfaces are approached, it creates incredible vistas whether a-top a mountain or in orbit. It's explained in more detail and with screenshots here, along with how the engine also allows seamless transition from planet to planet.
Like all interesting Kickstarter projects, it's incredibly ambitious and donation is always a risk. The various updates they've made to the page since launching show they're a dedicated team and the fact they've anything playable, no matter how basic, puts them ahead of the pack. While what they're promising with regards to vehicles and character progression is original, creative games as a whole are well-worn and a layering of RPG mechanics might not innovate that. As always, have a good read through their plans before putting your cash down and be prepared for the long wait.