As a rule I agree, but I think in this particular case we do have a pretty good track record in China, and they do publish their 5 year plans so we know what their targets are. In this case it's more nuanced than just saying they're going to keep growing because they have been growing.
The growth rates are a strange entity to begin with. Mainstream Chinese economists expect that China's growth will slow down eventually as their overall GDP rises, analogous to other high-GDP countries. This usually goes hand-in-hand with stressing the need for a transition to more domestic markets and balanced production (i.e. less focused on export and building productive forces at the expense of domestic workers).
At the same time, since GDP just measures "the sum of all the crap sold" and because the commanding heights of China's economy are controlled by the CPC, it is possible for it to have a somewhat different trajectory than the other high-GDP countries, as all of those other countries are also the imperialist order, they structure their economies around extraction from the global south (a small number have been propped up by empire as bases for attack, e.g. occupied Korea).
Basically... China will be in somewhat new territory in its attempt to build a high-GDP economy with a balanced productive sector not dependent on massively unequal exchange. As others (maybe you?) correctly note, the USSR was on this trajectory, albeit at breakneck speed and with less overall productive development than China - and without the interdependence that Dengist strategies created.
The basic question will be whether China can keep making more and larger amounts of things and services that are sold somewhere. Part of this will be what prices they can charge, and whether they can be higher prices than now, and this will depend on domestic consumption and pay as well as the dynamics of exports, especially whether other countries can similarly develop productive forces or if they'll just go the more likely direction of being neocolonies that make simpler products and with less concentrated industry.
Personally... I have no idea. I just think it's new territory.