Halo will boost sales but no more than the $70 price cut with 2 free games they had last year. Price cuts are the biggest system sellers.
14M in one year? Did the 360 even do that? Might of come close but the X1 is no 360 in terms of sales.
X1 Slim, yes it will increase sales but only in relation to the demand it already has. Plus Slims only sell well because they tend come with a price cut. I can see the X1 hovering around $300 before the slim drops and the slim will have to sell for $250 or less for there to be a boost in sales it already has. Then of course the PS4 will also be having a slimmed version at a cheaper price to it will have to contend with that
The X1 is in a very weak position because its success depends on what Sony do. If Sony resist a price cut again this year then It could sell about the same as last year. If Sony cut the price this holiday (more than likely will) then the X1 will struggle again unless it drops price to sub $300. Basically the X1 has played more cards than PS4 while the PS4 has more to play.
If they do drop price then they are throwing away their cards just to stay competitive with the PS4. What happens when the PS4 finally gets Uncharted, GOW4,Gran Turismo and TLOU2? Sony also have Street Fighter as a permament exclusive.
I also think E3 will be a battleground for 3rd party exclusives and the X1s success might depend on if they can get some major deals and hope Sony aren't willing to spend big bucks on more exclusives.
And why do you think Uncharted was pushed back and delay announced so soon? Probably tactical reasons. Price will more than likely happen this holiday ($350 maybe) and if they released UC4 and had a price cut they are effectively wasting an advantage especially if they can't keep with demand. Splitting the price cut and UC4 up will see strong sales over the holiday with UC4 to help with the strong PS4 sales after the holiday.