So to date, Halo 5 is around 3.5 million retail sales. Now that is WAY down from Halo 4 or 3, but I consider it well still. Now I personally expect 7-8 million LT, for one reason. It has good legs. Now lets look at the closest game matched to it, Halo 3 ODST. Now for its first week, it did 2.2 million. Halo 5 only did 1.5 million. Yet within a 10 week span, Halo 5 is at 3.45 million, Halo 3 ODST is at 3.66 million. So clearly we know which has better legs. And I know... I know... I'm going to say this, digital is also something Halo 5 has. Now say it or don't, many games are seeing shifts to digital, slowly but surely. Now most say its 20% for games, so we'll use that metric. Now I'm too lazy to do the math, but its close enough to 4.5 million. That quite a bit ahead of ODST, on a considerably smaller and fanbase, and one that is more weary of Halo.

Now Halo 4 did 7.5 million in its first 10 weeks, and ended up with 9.5 million LT. It didn't really have legs, and its userbase dropped like a rock. Halo 5 is doing better holding its userbase, and it is a better game in my opinion (yours may vary). So its doing ok, still quite low for a mainline Halo game, but not terrible. I think it will recover, and if Halo 6 is really good, it could help put Halo back into a good position.

I'd say 7-8 too considering how much the X1 install base will grow in the next few years...

Well, we have to remember that on Black Friday weekend, HALF of all the games sales were digital. So I would say it's probably at least 30% which would put it at 4.5 million.

I know many users and all the retailers do not like me saying this, but I see no reason to buy physical (unless it's a fetish or you are a collector or slow internet/caps). PC games sales are nearly all digital, why should the consoles hold back.

Especially they way you can quickly switch between games on the Xbox One, it makes more of an incentive to buy digitally. And people do, even if it's a little bit more expensive.

So I think Halo V will continue to grow. I haven't even bought it yet (A great deal for The Witcher 3 came up first) And I think it will have great legs - but most of those legs will be digital.

I'm not saying your wrong, but where did you get this from?

Reported right after that weekend in some industry journals and business management. 

It might reach 7-8 million this year if it's the main cheap bundle this year/holidays. Gears of War sold more than 1.5 million on the US alone during November and December .
If it didn't get bundled, which I doubt, I think it will finish with 6-8 million.

7m sounds about right, but remember all games are having better digital ratios. Its hard to compare digital without concrete numbers so its not too unreasonable to not care about them. 10-15% last gen became 15-20% this gen whoopdido. I have a feeling that almost every exclusive game is going to have amazing digital sales now, even though we don't get concrete numbers.

~7m

I think that's a fair assessment