Actually I think it looks right. India's population will be much bigger than china's by around 2050, even with this math, India's per capita PPP is still only about half of China's. Conversely, China's per capita GDP would be approximately half of the US in the same time frame. China's GDP per capita of 5x that of India's was never sustainable in the long term, although that is more a factor of Indian under-performance than chinese-over performance. I think what's more interesting is that whereas the combined US+India GDP is significantly greater than China today, the gap becomes smaller by 2050.
Using PWC projections, (without opining on their validity), GDP at market rates of China+Pakistan was 69% of India+US in 2020. By 2050, it narrows to 85% of US+India. The best way to think about it is a US alliance with India cannot offset its own power decline, since while india's economy will certainly grow (and will become faster than China eventually), the fact is china's current economic base is so large even if India was to boom for decades it wouldn't be able to catch up.
The other thing is that China's likely allies will also significantly outgrow the US and its 5-eye partners year, and have likely comparable rates to "high growth" india. While this is more to their lower base (i.e. for Pakistan, Bangladesh, Iran, Myanmar, Turkey), long term power will still shift towards SCO under all scenarios.
