It would have to be on a direct collision course, which would still lead to those stats that would be represented in scientific notation due to how unlikely it is to occur.
They will float until we intercept them in a thousand years, or their atoms begin to decompose
Not neccasarily. You have to remember that space is expanding. That means that eventually the probes would undergo the big rip where they are torn apart. Prior to that however, they would be so far from anything that it would be impossible for them to interact with anything.