Is there a way where we can update a product and have it flow to the user?
For example, if they ordered a product that had 3 courses assigned to it, and we add a fourth course to that product - can the previous purchasers receive that update?
It didn't work in a test, however I'm not sure I set it up correct if that is possible.
No it will not work like this.
If 3 courses are connected to a product then only 3 courses will be assigned to that user when she purchases it. Now if you connect another course with the same product then only the new users who purchases it will get access of 4 courses.
If you want to give access of the course to old users also, then use membership plugin to create memberships and make your users purchase memberships.