In the long run, not much can stop China becoming thoroughly pre-eminent - if not necessarily the unchallenged global hegemon with complete freedom of action it aspires to be. But in the short- to medium-term its progress could become a lot bumpier than the exceptionally smooth and untroubled run it has managed over the past two decades: and things might even go binary on China in a way it won't much enjoy.
The acid test for Xi in my mind, and probably in his too, is Taiwan. It's abundantly clear Xi wants his crowning glory to include the "re-integration" of Taiwan during his own regime, and has probably vowed to do this by whatever means. But he'd doubtless consider the need to resort to violent re-annexation as very much second prize. There must be many more examples of things he'd much rather didn't go wrong, along the way to the Chinese Dream being fulfilled.
Up until very recently, from the outset of the Chinese march towards their Authoritarian Capitalist successes, the Chinese have proceded emolliently, if not actually by stealth. If Hong Kong had remained placid, one might have imagined this course would have been continued - just look at the gains they've made! By all accounts they've pretty much annexed New Zealand as a mere commercial dependency, with Australia firmly in their sights and already well under the thumb. In lockstep with the commercial hooks, the political grappling irons have also been steadily applied, along with bribery, corruption, and flooding with fee-paying students - little trojan horses by the tens of thousands. There are any number of chilling accounts to be found, not least the way in which Chinese citizens abroad are monitored (and indeed directed) for their every action. China does what it fancies with the Uighurs and narry a Moslem leader mutters a word. We haven't even mentioned espionage, massive attempts to corner markets in raw materials, building artificial islands in the South China Sea, and implanting high-tech trojan horses in the UK's telecomms and electricity infrastructure. But, for the most part, this has been achieved with only modest push-back, resistance, or even friction; and mostly (to be honest) grovelling, money-grubbing acquiescence. (What an epic shit Osborne is.)
The sheer power amassed by Xi in every dimension is formidable indeed. And with it, inevitably, grows the temptation to call a halt to the disciplined habit of swallowing pride, and turning the other cheek, when setbacks and annoyances occur, as China has chosen to do many, many times in the past**. (Cultural obsession with maintaining "face" doesn't help much, either.) So now Athens can no longer forbear from lording it over Sparta, and from forcing every other nation choose between the two++.
And look what's happening today. The kow-towing era of Osborne / Cameron / May has come and gone. The fates of Hong Kong and the Uighurs are a now serious issues around the (western) world, largely impotent even as we are. Australia - yes, Australia, dependent as it is on exporting raw materials, is stirring against recent developments. And there's talk in the air of Japan joining the Five-Eyes community. That's of gigantic significance - Japan is as good an "unsinkable aircraft carrier" as the UK was vis-à-vis Russia, with a very desirable set of special capabilities. Altogether a rather different turn of events in that neck of the woods than one might have anticipated a year ago, when much more likely seemed the expulsion of NZ for having been thoroughly subborned by China and no longer trustworthy (with Australia very much on notice).
What does China have to fear? In the grand scheme of things: not much. Trump could press the Red Button tomorrow: but the man holding the briefcase would smile and say, sorry Mr President, it doesn't seem to be working today. Ain't nobody going down that path unless Xi does something unimagineably crass. A few minor economic hiccups arising from unforced errors, perhaps (as opposed to the ones they are inevitably going to suffer along the way in any case).
Most importantly, if Trump thinks the power of US sanctions will hurt China as fundamentally as they've hurt Iran, to the point where maybe he might dream of precipitating domestic unrest; well, I'd guess the CCP's web-enabled 100% Big Brother regime is more than capable of 'defusing' the social consequences even of some otherwise serious short-term economic setbacks. Not many nations spontaneously combust during recessions anyway; and few have the kind of omnipresent, omnipotent fire brigade that Xi has at his disposal.
No: mostly it'll be delays to Xi's grand plans; infuriation as Taiwan
shrinks ever further from contemplating a voluntary reunion; plus, of
course, Loss of Face as some of the global prestige Xi
fondly hoped to deliver over the coming years evaporates.
That could be pretty bad for Xi personally - if only for his private equanimity: but he's just one man among a billion. Objectively, the worst case for China is that the world polarises into camps, Cold-War style, for 50 years - instead of more-or-less peacefully slipping into his Belt-and-Road vision of China as Top Nation with Xi beaming benignly as every nation hastens to do his bidding, and China resumes its destiny as Centre of the World, and undisputed Greatest Culture On The Planet.
So: today, I'd say that particular rosy-for-Xi outcome looks rather less likely than it might have done just 12 months ago. Polarisation it is. Tough titty, Xi - but you had it coming.
** I always think of Libya 2011 and the casual overthrow by the western powers of Gaddafi, essentially a Chinese client at that stage
++ And we know what happened then ...