I don't know if either is gonna reach 50 million so no answer. the systems are too similar, and too many games are being multiplatform to keep people from having reasons to own both.
And I just don't see how last gen we had 120 mil PS2's 30 or so Xbox and 25 GC.
And now your expecting to see 100+ wii's and then some 50+ for each 360 and PS3. Not gonna happen
seems like 360 has been sitting around 20 million for so long. and PS3 is only at like 16 million.