This is very much along the lines of extended functionality we are wanting to add to the cart.
The "Upcoming Products" or "Expected Products" block could be implemented quickly. What has delayed it thus far is the implementation of the inventory management systems. This is a major focus of current development. While we have a rapid need for completing the product kit and package systems, the infrastructure necessary to manage expected products using this system rather than the product system alone is coming along nicely.
At this point, relationships between inventory items and product objects are not completely fixed, but as soon as they are you can expect generation of display systems to meet this need.
David