Too many unknowns to really get any firm idea on what the deuce is really going on in terms of total sales.
Some thoughts :
Halo 5 is not a failure (duh) by any reasonable perspective. However, it may be in decline in terms of unit sales.
This PR release isn't really that different on the whole than previous first-week Halo MS PR efforts.
However, there are a few things that are odd, like :
They say Halo 5 software and hardware. What does that entail?
Definitely :
$60 Retail Game
$99 LE Game
$249 Super Mega Game
$500 LE Bundle
Possibly :
$70 Controller?
Headset?
REQ Packs?
And then you have the fact that a decent portion of the 'retail' sales could be counted as 'Digital' due to them being just codes that you have to redeem and download online (LE Bundles, etc).
Anyway, we'll know more as time goes on.
My guess : the series is in a slow decline, but still will have outstanding attach rate and a core fanbase that will still be fairly strong by the time Halo 6 comes out. People have to remember that ALL mainline Halos seem to sell in the same general range of ~10M LTD, plus or minus a few million from beginning to peak to decline. So if Halo 5 sells 7.5M LTD + or - a million or so, that's still a pretty big deal.
I don't know what kind of legs it will have though. This isn't 2007 anymore, there are FPS's coming out of our ears, and a bunch of them are about to drop that may cut H5 off at the knees in terms of attracting fans outside the core day-1 types over these holidays and beyond.
Any potential X1 FPS fan buyer on the fence certainly is not very likely to buy a $500 bundle when they could grab a $349 X1 with whatever game and snag Blops3 or Battlefront for roughly $100 cheaper.