The biggest request we've gotten for new products is for enclosures to fit the CR-10 S4 (400x400x400) and the CR-10S5 (00x500x500) models. Its not as easy as it sounds, since those two are the biggest 3D printers on the market. The S5 is so big it looks like its going to take up an entire table!
The first beta out there is the S4, since it makes sense to gradually make the design bigger. Its bigger than the standard model, going from 27 to 35.5" deep, from 22 to 25" wide, and a little taller. We shipped the first beta this week, and are anxiously awaiting feedback to see how it works in the real world.
You can currently purchase the S4 beta on the website. Please be aware, though, that its still a beta: you'd be one of the first to get the new model. Although its been assembled and tested by us, it hasn't been used by that many customers, and so we'd want your feedback on how well it works, and you never know, some parts might need to be replaced or redesigned. (In which case we'd ship you the new parts for free.)
You can really get a sense of how much bigger this is than the standard CR-10 from the side view: