Somebody: As far as I can tell, this is pretty much an evidence-free assumption your part. China and Brazil just *quadrupled* their GDP per capita in the last decade, with India not far behind. In other words, from those three countries alone something like 2.7 *billion* people saw a massive improvement in their basic living standards.
When are those "current physical limits of the world economy" supposed to kick in? On the contrary, it looks more like if there are any limits on growth rates, it's in industrialized North America, Europe, and Japan.