So far as China's imports of Australian energy commodities are concerned and taking a long term (20 year) view, a few points.
Any developed economy needs a source of energy, and practically all economic activity requires energy in some form. This is a given. So long as China's GDP remains stable or growing, they're going to need some way of powering it.
There's a few options, eg locally we have WA and the NT heavily reliant on gas, we have Qld, NSW and Vic heavily reliant on coal and there's Tasmania with it's hydro power. And that's just for electricity, heat etc. There's also transport, primarily fuelled by oil in most places (including all Australian states and most countries overseas with very few exceptions).
A few facts and figures about China's energy use at present:
18% from oil, of which 10.5% is imported oil and 7.5% is domestically produced oil (production of which is fairly flat). China's proven oil reserves are equivalent to 16 years' of current domestic production.
4% from gas, of which 1% is imported gas and 3% is domestic gas. China's gas reserves are equivalent to 32 years of current domestic production.
6% from hydro, which represents about a quarter of the hydro-electric potential in China (that is, three quarters of it is undeveloped).
1% from nuclear, wind, solar etc.
71% from coal.
Now factor in that various forecasts suggest a doubling of China's energy consumption over the next 20 years. Refer attached image (source = Energy Information Administration (US Government)).
It's hard to see how China could actually achieve such growth without an "all of the above" strategy. More gas, much of it imported. More oil, most of it imported. More hydro to the extent that they can build the dams quickly enough. More nuclear. And yes, most likely more coal as well. Take coal out of the picture and you'd need absolutely ridiculous levels of growth in LNG (gas), nuclear and hydro which probably aren't achievable in practice.
So whilst I can see short term fluctuations, unless China's economy falls in a heap they're going to need more of everything so far as energy is concerned. Unless they can ramp up domestic coal production (maybe they can? They already produce about 50% of world output) then that's good news for Australian exports of LNG certainly, uranium probably and possibly coal too.
It's not so good for the environment of course, but this is the AUD thread not the climate change thread.