When Sony, Microsoft or Nintendo introduces a new videogame console, its obsolescence within six years is more or less assumed. Nintendo is likely to release the new Wii U later this year, and other console makers are rumored to be working on next-generation systems. But as early adopters line up to experience whatever new high-def graphics those systems may offer, the next-next generation of console is already gaining momentum. The device is the smartphone, and within a decade it could be powerful enough to replace conventional game systems for good.