You know why they stop that extrapolation at 2080? Because if you go to 2090, it claims Canada's 120% Muslim.  Obviously it has to plateau out at some point, and that will be much earlier than 2080. 

The problem is that exponential and linear growth look very similar at their early stages, but demographically, the latter is what is actually happening. Go from 1% to 4% in 20 years, yes, that's a quadrupling, but it's also an addition of 3%. Going forward another 20 years, you're not quadrupling it again to 16% ... you're linearly adding 3% to 7. 

Put another way .. let's say you take in 10,000 migrants from country A. Next year you bring in 10,000 more. The numbers have doubled! An anti-immigration publication might extrapolate that and claim we're going to be 50% Aian within 12 years! When in practice, you're only taking in 10k a year linearly and 12 years down the line, you're only 130,000 or less than 1%.