That number only makes sense of people are unable to reproduce as they age. There is probably no correlation between population growth of mortal humans and immortal humans. They may have 100x more children, and they may have almost none. You can't extrapolate after such a bifurcation in the model.
In 5000 years the human race might be multi-planetary, or extinct. We have absolutely no information to make such predictions or even estimate their likelihood.