Hardware sales are entirely the responsibility of the console manufacturer ...
Game publishers buy development kits and pay a licencing fee to have access to the hardware in order to sell their games to the console's userbase; in terms of the publishers, the product that Nintendo, Microsoft and Sony are producing with their game consoles is a large userbase which can support game development. Sony, Microsoft and Nintendo heavily market their userbases begining far before a console is released in order to attract publishers ... If they fail to deliver on the promised userbase a third party publisher should/will look to another platform to deliver their product to.