r is not intrinsically a result of g, even if they are "supposed" to move in lockstep. The soviet union had g without corresponding r. A high g just makes a high r easier to stomach.

Inequality doesnt really have an inbuilt limit as such and we are still a way off people owning entire countries, which wouldnt be without historical precedent.

Of course, it's not forever, and Piketty's conclusion that capitalism is not viable is wrong because of that.

But it can last for a really long time, and if something lasts for more than your lifetime, do you really care that it's finite.