In terms of the US, sure.
Isn't the gap like a few 100k? A Black friday victory and the Halo launch could easily balance the current difference if so. Add in a slight advantage over the holidays and then you have X1 winning 2015 in the US. Not saying I expect it to happen but its very possible
Gap is somewhere near 800k (770k?) according to the guru Zhang who keeps the best track I've ever seen of this kind of thing.
The way I see this is simple :
PS4 stays $399 = X1 ties PS4 for 2015 US Sales
PS4 goes to $349 = PS4 moderately wins total 2015 US Sales
PS4 goes to $299 = PS4 murderbaths the X1 in total 2015 US Sales