Forecasting the doom of China has become quite fashionable since the '90s. I'm not saying that China's hegemony in the future is inevitable, but there's a lot of confirmation bias in these reports, the absolute majority of which come from the United States and sometimes prioritise the pleasure of their readership, at the expense of sober examination of hard data. Political science is, together with psychology, one of the most fluid domains of the humanities and there are quite a few instances of history, statistics and finance getting abused by the authors of these reports.
Goldstone had been certain for the upcoming demographic catastrophe of China, but what suffered most was his reputation as a scholar. My favourite is
Gordon Chang, who was convinced that China will collapse in 2006. Then he revised his hypothesis and opted for 2011. Then 2012 would be the year of the (Mayan) Apocalypse. Or maybe 2016. Definitely
2017!
As for diplomacy, China has plenty of allies and they increase, respective to her economic power. The aforementioned analysts usually portray it as international blackmail, but it's a much more reciprocal procedure. The investment and loans are beneficial to both sides. Not everything is rosy, of course, but, despite any sporadic issues, the trend clearly shows the economic expansion of China, especially in her immediate periphery, which then results to international cooperation. It's not a pioneering tactic either. The United States themselves heavily relied on the same strategy during the late 19th century and the Cold War, especially when the United Kingdom was essentially too bankrupt to maintain its sphere of influence. Wealth is what determined the allegiance of Egypt, not the public image of the Soviets. That expansion was of course marked by basically the same problems, like predatory practices, collaboration with shady regimes, implicit or more direct interventions etc., but the overall result was successful.
That being said, economy is one side of the coin. Philippines reconsidered their policy towards China, because the US under the Obama administration were too weak to guarantee their safety, Cambodia also cooperates with China, becauseo of Vietnam's aggression and Chinese investments and East Timor seeks an alliance with the Chinese, in order to protect itself from Australia's attemts to rob it from its natural wealth, while there's also distrust against America, because she had greenlighted Indonesia's conquest and annexation of the old, Portuguese colony, leading into the genocide of hundreds of thousands of civilians. These are just a few random examples, with the exception of the strongest countries, like Japan or India, whose interests still clash with those of China, most of the countries in the eastern Indian and western Pacific oceans have established friendly relations with Beijing. If Chinese strength continues to increase and that of the US to (relatively) decline, then even the stronger players may reconsider their priorities and decide that cooperating with China will be more beneficial than antagonising it.