Practically speaking, keeping 100% of the ice off of even well-used sidewalks 100% of the time all winter long isn't going to happen. All it takes is one patch of black ice and you can have a very serious bike crash.
There's also a safety issue in that if you're in that kind of cold for long enough, it'll kill you, jacket or no jacket.
Bikes are but a means to an end: decreased traffic, reduced urban pollution and safer streets. Getting more people on bikes means fewer people on cars. Reducing traffic also require good and frequent public transport for both people of reduced mobility and weather events. Most situations were buses or trains are disrupted is a time when driving isn't quite safe either. And cars aren't going to go away, what you want to do is affect the margins: the 2 mile drive to get milk that would 1) ideally not have to be 2 miles and 2) trivially cycleable in safe infrastructure.
I am also of the belief that increased density should be a goal, for multiple reasons, which would make the need of 60 minutes commutes unnecessary for most, with the lovely side-effect that people that desire a suburban lifestyle can still have it and the equation for both bicycles and public transit a no-brainer.
There's also a safety issue in that if you're in that kind of cold for long enough, it'll kill you, jacket or no jacket.