You could say that about anything! Why not build a subway now, before the population doubles: it will certainly be cheaper to build a subway now than in 30 years (when we'll have the necessary density).

Why not double the capacity of all our water mains now, before the price of pipe goes up.

Construction inflation is a fact of life: it doesn't mean we can afford to neglect our current needs to build light rail and trolley across the entire city.

Light rail is not the future; it's just a very expensive way to move a small number of people.