It's not going to be so simple for China going forward. Every aspect of their growth will get a lot more difficult, including that switching to a services dependent economy is dramatically slower growth than what you get from filling out extreme slack in a very backwards economy that hasn't fully industrialized (China circa 1980s & 1990s).
It doesn't matter how many people you have on the inside in isolation. It matters what the output per person is combined with how many people you have.
China is running into an increasing blockade with its largest trading partners, as they recognize China has been playing the game one-sided for a long time (to say nothing of the rampant state-supported dumping). It's still illegal to acquire the majority ownership of a Chinese company as a foreign entity, 16 years after they joined the WTO.
It cost China $40 to $50 trillion the last ten years, to grow as they have. The return they're yielding on each dollar of debt has long since gone below 1 to 1. Now their households are rapidly taking on large amounts of debt. Their corporations are the most indebted on the planet. It's a trick that can't be duplicated in the next ten years to keep the magic growth machine going.
In the span of ten years, China caught up to the US in terms of total debt load as a percentage of GDP. S&P is projecting they'll expand that by a further 77% by just 2021. That would entail taking on another $25 to $35 trillion in debt, in just four years or so. To put that into context, in four years they'll add roughly ~$3 trillion to their GDP; can that amount of economic expansion fund another $25 to $35 trillion in debt? We'll soon find out (by another contrast, the last $25 to $35 trillion in debt they took on, coincided with $8 to $9 trillion in new GDP; while high, a $3 of new debt to $1 of new GDP ratio sure beats a $10 of new debt to $1 of new GDP ratio).
Their large foreign reserves used to be a safety offset to their debt. Except now debt has grown ~15 fold beyond the $3 trillion they have in theoretical reserves and is still rapidly expanding while their reserves haven't net moved in years (with at least half of those reserves already spoken for).
They're well aware of this dangerous situation of course. Which is why they're attempting to slow the growth of debt, but they've entirely failed at that:
https://www.cnbc.com/2017/11/26/chinas-deleveraging-debt-sti...
And this vast collection of debt has happened while China still almost entirely lacks an actual entitlement system similar to developed nations with the highest standards of living (such as Sweden, Germany, Denmark, Canada, etc). I don't see how they can ever afford that, if they're already starting from a position of such extreme debt entanglement. As their population ages rapidly, they'll find a far greater need for those types of systems, and it will further drain their growth potential by siphoning growth capital (up to now, China has gotten a free ride on that aspect, they've had to devote very little capital to such things as a total percentage of their GDP or budget).
Probably the only reason China is still chugging along with growth at this point, despite the mounting problems, is that they've done a pretty great job learning from other developed economies. It has helped them get huge at warp speed without tipping over. They expended a lot of effort on studying other major economies and their central bank systems. If anything gives them an opportunity to not fall into the Japan-trap in terms of debt and growth, it's that willingness to learn fast, adapt fast and rechart the map quickly if needed (when it came time to change course, Japan refused, they kept piling up debt even after it crushed their budget and savings rate; they kept over-spending on public works even as the return on investment went negative, and they entered a repeating cycle of making the same mistakes over and over again for years as it increasingly trapped them in a huge debt spiral).