Probably when people are so mixed racially that you can't differentiate it, is the stage at which we stop referring to groups by their ancestry. However, at that point it's possible that newer large groups of immigrants will be arriving, and they will be a distinct group.
From a historical perspective it's interesting. I took a class on the History of Toronto and we devoted a long section on different immigrant groups and their experiences in Toronto, Chinese-Canadians, Italian-Canadians, Irish-Canadians, Jewish-Canadians. Back then, different groups had very different experiences and faced discrimination and discriminatory laws. For example, some stores would have signs that say "no Jews".
Today, there's obviously much less overt discrimination, but you can still look at various immigrant groups and trends. You can see that a lot of Chinese immigrants are settling in Markham or Scarborough for example, it's quite visible by the stores, the people and the language they speak. On the other hand, some people of Chinese descent are pretty much completely integrated with Canadian culture, so the integration process is happening.