Realized I haven't made a prediction in my own thread:
In many ways, China is following the Taiwanese/South Korean model of political development. The early stages were dominated by one-man/one-party dictatorships, later gradually liberalizing to the point that genuine democratic elections were made possible in forty years, but not before Taiwan and South Korea had become industrialized and developed countries in the 1960s and '70s. It is not out of the question that by 2020, China should have become politically liberalized enough that democratic elections could be held. The 'Great Recession' that is occurring world-wide could well hasten this process, particularly if India grows at a higher rate than China.
Why would India growing faster than China lead to democracy? If that is what you were trying to say.
Think of it this way: India and China are both rising powers -as well as rivals (at least since the Communist conquest of mainland China in 1949). As long as China sees itself growing at a faster pace (particularly at a time like this) than any other country in Asia, it will see its model of 'authoritarian capitalism' vindicated -and would further delay any chances of political reform. If, however, India (as the world's largest democracy) not only catches up to but even exceeds China's rate of economic growth, that could well help to spur calls within China (and the CCP) for greater political liberalization. I am not saying that India alone will turn China in a more democratic direction, but combined with forces within China and the Chinese Communist Party, I fail to see how it won't.
Edit: I see Verily has already pretty much made my argument.