According to the March developer stream, they are doing something on the order of 10,000 bridges.
In a previous stream, something was said about not doing every single bridge. And by that, they meant – and these are my words, not theirs: Don’t expect that little overpass by your house to be done.
But, 10,000 still sounds like a lot. Maybe with iteration n of the World Hub, people might be able to fix the overpass by their house.