There are very few data on immigration by Canadians, be they Canadians born here or outside the country. This is because we are free to leave Canada without having to leave a forwarding address.
However, there are a number of studies conducted as part of investigations that have established that a number of immigrants leave our country, either to go to another country or to return to their countries of origin. Take Hong Kong, for example. It appears that many Chinese who came here in the 1990s returned to Hong Kong a few years later to continue to do business in their country of origin.
With regard to future immigrants, it is quite true that China, with its one-child policy and economic boom, may cease to be as significant an employee source as it has been for the past 15 years. However, many other countries could contribute to Canadian immigration. For example, the countries of the South Asian sub-continent are already a significant source. There are countries in Africa and the Middle East where demographic pressures could remain high in future because the birth rate is still high.
In future, source countries may therefore change. It is also quite true that we compete internationally to recruit immigrants, because all industrialized countries find themselves with the same demographics we do — rapid aging of the population and few young people to replace retiring baby-boomers. Nonetheless, there are still source countries. Canada might have an advantage in that its immigrants have always been highly diversified.