The LEGO Cuusoo site has announced that the Masashi's Back to the Future III Jules Verne Train set has made it past the idea stage and will movie on to the review stage. Basically Masashi's set was able to obtain over 10k supporters so to the Review stage. A "LEGO Review Board" composed of designers, product managers, and other key team members will examine the idea. We'll build concept models and determine if the concept meets our high standards for what it takes to be a LEGO product. This includes factors such as playability, safety, and fit with the LEGO brand. Every potential LEGO product goes through a process like this and must meet the same standards.
The review process will being in May and go through September. If the set survives the review process and is green-lit it will then move on to the final stage which is known as the developmental phase. During this time, LEGO model designers refine the product and develop it for release, we create the product materials (box, instructions, marketing), and get everything ready for a production run.
LEGO has already released a DeLorean Time Machine through their CUUSOO program. Check out images for Masashi's Jules Verne Train entry below.