Currently there are many databases that contain STL files with the intention of being shared and printed. Website like thingiverse.com have thousands and thousands of models that you can simply download for free and print. On these websites you can find a wide variety of things ranging from small tools like a wrench or scissors to toys or other useful knickknacks. Every day people are adding more and more STL files to websites like thingiverse and as the community grows the quality and quantity of content and practical creations is increasing.
I envision future software for 3-D printed construction that is the one stop shop for all of your construction needs. This software will contain a seemingly limitless number of models that can be 3-D printed in the concrete. There will be models ranging from fireplaces and fountains to homes, stores and office spaces. People will be able to browse through these models, purchase them and have them printed in under a months time for cheaper than previously imaginable. This website or application will also include an editor feature. This editor will allow you to modify existing designs to your liking or create your very own from scratch. This is much easier said than done because there are some limitations to 3-D printing in concrete, the largest of which being that you cannot print in midair. Concrete must be laid on top of something or else it will simply fall to the ground. It is very likely that some architects will fight to keep this software from becoming a reality.
If you can create a software that guarantees structural security of a building then you largely eliminate the need have an architect at all. Software like this will empower the average person with the ability design a home to their exact liking and customization.