Yes. Assuming the Xbox One get to 11 million on chartz, the PS4 will get to 19 million regardless so the gap is at least 8 million. So the total gap at the end of this year should be approximate to the Xbox One YTD totals. This may be a good rule of thumb actually.
So let's disagree of OP and say it already have 9M and should be 10-11M by end of March.
Your bet is hilarious btw. It seems to involve miricles, paradoxes and quantum tunneling.
The other partie run of the bet after making the claims...
And it involves all that, but is just X1 vs PS4 globally in USA, no WW involved as the user already accepted that will never come true.