From a Business Standpoint, How long should Nintendo and Sony continue on with their Struggling Systems if they continue to do the same?

[Osc89]

I imagine they will both stick it out for the normal generation length, and both not bother with a traditional follow up. Nintendo have already merged handheld and home console departments, so they with probably go into the next generation with a hybrid console. Sony will use Gaikai to spread games to all of their products, while making a line of PS phones that are essentially the Vita successor.