Did you factor in the rapid decline of the Chinese population that is baked in? Just math at this point with such low birth rates for a very one time.

I doubt it's that relevant, provided that income per capita continues rising faster than in the west for a while yet. Which seems pretty likely, given the low base. For a place with slowly growing typical real income per capita like the US, the demographic effect is a more important part of the calculation of the total GDP trajectory.

I doubt there are any forecasts of the US economy once again becoming larger than the Chinese one at constant prices this century. There are quite a few people in China, and (to overgeneralize) they do not have a reputation of not wanting to get ahead. Of course the future is uncertain. Chinese real GDP per capita was about a third lower in 1850 than it was in 950. And revolutions do tend to set things back, for example, and they're possible anywhere.

Jim