MS and Sony need to make sure that these new systems have full backwards compatibility. I think that the majority of people out there are content with the current gen. The shift to the next gen will not be as rapid, because like others have said before, the graphics quality is already good enough for most. The next xbox should be able to operate as an xbox 360. Meaning, full compatibility, including software, the controllers and other peripherals. Kinda like every new iphone. Eventually, more and more people will move to the newest generation, but it will still be easy to cater to the Xbox 360. This works out good because most developers probably don't even want to make the switch yet, but I'm sure that there are some that do.
My guess is that it would take around 2 years for the next generation consoles to become the current gen. The next generation, however, will probably end up being even longer than this gen.







