Not too sure what point you are infering to - if you meant labour are disappearing as
construction/infrastructure boom is ending - I think you are under-estimating chinese appetite for property investment. It is almost ingrained in the Chinese culture to invest - and as China go from the old agarian culture where saving and putting money in the bank is the "right way of investment" to the modern property investment (and even stock market), the demand for property will continue. Not to mention China still plan to build another 8000 km of HSR and linking up those HSR with the surrounding countries which are under the AIIB/Silk Road plan. There will be more infrastructure, properties/cities to be build along those town connecting / along the HSR lines.
Secondly, as China tech up, it will become even more energy hungry than before, and more people will go into the energy sector - which means more coal miners (even though Chinese authority are trying to shut them down but as reality of energy requirement hits) and workers in mining sector. More workers to build energy infrastructure - power plants, power lines, delivery systems...etc. And even more workers to maintain these infrastructures.
It doesn't matter if wage is rising - the labourers are barely catching up with the CPI. And they will soon hit the middle income trap as companies and corporations looking for cheaper alternatives (like the news indicated - robotics....or moving factories to third world countries) to maximize profit. This will in turn create downward pressure on wages - as seen in Taiwan, America, Japan... where wage largely stagnated or even going backwards.
I have recently visited China and the Chinese I have talked to all said the same thing - you can't survive on one labourer wage alone and nevermind retirement! The biggest problem with this is that majority of migrant labourer are poorly educated, and being aged worked (in their 40s) means the prospective is extremely limited - they can't be expected to go back to school, nevermind going to university to get a degree. It is precisely because of this they will be trapped in their predicament as labourer for the rest of their live. If they are smart - they might save up and invest by opening up shops or restaurants, but China's business/service sector is already highly saturated - if you ever visit China you will see what I mean - shops are opening up and closing down due to intense competition on daily basis.
Now - about nannies - remember the current chinese predicament of young couple not wanting kids?
There will be so few kids for large pool of people who wants to be nanny which only means more unemployement. Not to mention as China tech up and modernize - there will be more requirements for workers to get "licensed" or certificated which means a large portion of them won't be able to do as they can't afford to go to school (can't afford the time, nor the money).
Also, remember the problem we are talking about is
NOT the younger generation where they have the options and the education - the problem we are talking about is the older 40+ yr old migrant workers with limited education. LIke I said previously - as China becomes more affluent - they will want their nannies to be "certified".
Now, you bought up an excellent point!
Perhaps that's a cheapest and most economical policy Chinese government can implement.... to encourage even more smoking and drinking by opening up more bottleshops and liquor stores and create more liquor factories to make it cheap and plentiful!
As these 40+ yr old's prospect become dimmer by the year majority might hit the bottle and thus shorten their lifespan. The Australian government did it before - allowing cheap and plentiful of liquor to flow through aboriginal community and it devastated the aboriginal community as average life expectancy is less than 70 (10 years lower than non-aboriginal). But the problem with this of course is what kind of social impact it will bring when liquor is plentiful. High crime rate, traffic accidents, domestic violence.....it won't just kill the older 40+ generation, it will have collateral effect on the "valued" middle and upper class too as they too may fall victims to them (or victims to the disenchanted migrant workforce). So it will create a breakdown of social order.... not an ideal solution.