Population of the GTA is expected to increase by almost 50% by 2041, with the bulk of that in the 905 (mostly in York, Peel, Halton).
https://www.fin.gov.on.ca/en/economy/demographics/projections/#s3d
While expanding GO Train capacity is good for accessing the 25% or so of GTA jobs that are in the downtown core, it is inevitable that Highway expansion will be needed for the rest.
Not to mention, 50% more population growth means 50% increase in people
buying stuff. This means many more trucks on the road, which this highway is well suited for.
I'm unclear why a highway makes sense, but suburb-to-suburb GO rail does not?
I would rather see, in the fullness of time, a GO rail corridor in the 407 ROW and even the 401 ROW, with tunneling where useful to take the trains slightly askew to serve destinations.
I likewise am happy to support a rail connection following the '413' alignment; provided that existing demand supports it.
I don't think growth need inevitably be outward.
I think we could sustain the vast majority of growth within the existing urban footprint and we would be better off doing so.
In which case that's where the greater investment in transportation infrastructure will surely go.
While cars in some form will undoubtedly be with us for decades to come (or longer), I strongly suspect they will all be computer driven in dense urban areas.
That will allow for far greater efficiency in the use of highways in particular and the road grid more broadly, which should reduce demand for additional lane capacity.
I don't see the 413 as the answer to congestion, anymore than the 407 was, or the 401 before it.
They were both proposed as solutions to congestion, and managed to bring more sprawl and traffic without ever addressing the issue they were initially targeted towards.