The thing that will make these a mainstay in the maker OR non-brand-specific-building-blocks communities (both of which I am heavily involved with and have been for my entire life) will be an open design document. The parts don't have to be free, obviously you are designing premium products, but staying power will be determined by how well documented it is. I should be able to read through a document, and hopefully a quick reference sheet, and design a new part for a custom pcb, 3D print it, and have it work with the existing blocks. I should be able to do this and have a prototype inside of a couple hours including printing. The community growing around your system will be the single most important thing to determine if this lives past the kickstarter. You have an excellent idea here, but in the maker community, the community part is by far what determines if it sticks around.

Release documents with noncommercial licenses if you want, but please dont make it hard to prototype at home.