23 million is more than a little optimistic. That would require from here on in an average of over 275K per week until the rest of the year. Its currently averaging I believe around or just under 100K a week in 2015. Personally I think it will hit somewhere between 20-21 million by the end of 2015, no more than that.
PREDICTIONS FOR END OF 2015: (Made Jan 1st 2015)
PS4 - 34M - XB1 - 21m - WII U -12M