A lot of truckers and travelers from the USA use the 402/401, 403 and QEW to bypass Lake Erie. Interstate 90 travels south of Lake Erie and is a longer, tolled route.
An extension of the 402 to Niagara Falls or Fort Erie would better serve these people, but due to the fact that they are simply using it as a bypass, I doubt it would be very practical. Also Americans don't pay taxes to fund a project like this. Maybe the USA could fund like 50% of the project since it would be a big benefit to them?
Living in London, this would be a great route to get to the Falls, which I visit a few times a year.
Politically though this is impossible. The route simply isn't cost effective, and most of the voters in this area are conservative. The municipalities are broke due to stagnant population growth and I doubt the Ontario Liberals (also broke) would ever give them this, and who knows if the federal conservatives will stay in power.
Nice idea though!