I'd be amazed if this doesn't sell over 1.5 million over the PS3 and PS4. I think it will do it quite comfortably when all is said and done. Your looking at 2 million plus all told I reckon.
PREDICTIONS FOR END OF 2015: (Made Jan 1st 2015)
PS4 - 34M - XB1 - 21m - WII U -12M