I dont think so. I think the general hardcore 360 crowd already exists. Its sales will start slowing this year, but still be solid.
The PS3 has more room for growth IMO.
But both consoles are so similar that people will only get one or the other, only hardcore gamers purchase multiple consoles.
And, I Should add, hardcore gamers are the minority when it comes to the general population.
I am not sure about 70 million. I did not personally see the 360 passing even 60 million,
but you never know.
My gut feels Natal will not be the success everyone thinks it will, but I don not think it will be an outright failure either.
You never know.