Microsoft Paint will be deprecated and thus not yet removed. Microsoft mentioned that Paint 3D is the successor of Paint, and as such, Microsoft hopes that people switch to Paint 3D. For that reason, Paint 3D will not be removed anytime soon, and if it does, it is very likely that Microsoft will create a new tool to replace Paint 3D.
That said, at some point in the future, Microsoft will remove Paint. This will happen in one of the major updates which is basically an upgrade to a new operating system. As a result, there is no way to stop Paint from being kept on the system automatically. It is likely possible to copy the executable to a safe place in order to use it in the new location, but you may need other dll's too.
My advice would be to find a system where you don't use Paint on, for example the pc of a family member who doesn't use paint, or a virtual machine on your own computer. Update windows with the newest update that is said to remove paint, then see if you can copy files over to make it work again. Once succesfully done, you can upgrade your own install and repeat the process.
Alternatively, consider alternatives, such as paint.net
EDIT: Microsoft has announced to move Paint to the Windows Store. In this fashion, Microsoft wants to keep Microsoft Paint available to everyone even after they remove it from the build, to compensate users for removing a feature people are not comfortable with seeing to be removed.