Can the XBox 360 total sales stay in front of PS3 total sales?

[hduser]

How would this comparison work if 360 stops selling long before PS3? Would we lump the next generation of the 360 in with the current 360 numbers? Technically, the PS3 will out live the 360 and probably surpass the 360 sales # but it'll be meaningless if MS counters with a say a Xbox 720.