Apparently, the Singleplayer campaign possibly got axed in favor of including a battle royale mode into the game

I guess that really would fit with it's tagline: "Forget what you know"

Sources:

Kokatu

Polygon

Charlie Intel

Would you still buy the game without a singleplayer campaign or any other singleplayer content to speak at?

From Charlie Intel:

This fall’s Call of Duty: Black Ops 4 will be multiplayer-only, lacking the kind of single-player campaign that has been a key component of the annual series for over a decade, two sources familiar with the game tell Kotaku, corroborating a report published earlier today at Polygon.

One of those sources also echoed a report from top Call of Duty information-broker Charlie Intel saying that the new game will have a battle royale mode. 

If the rumor is true, then the singleplayer would probably have been axed because otherwise there wouldn't be enough time to develop the Battle Royale mechanics and maps in time for the release of the game.

I'm the minority, but at this point I do not play COD's for their campaign. COD2,COD4, and COD:WAW had amazing stories, but I just do not care about Call of Duty stories anymore.

I'm all for a Battle Royal mode, with such a large budget it will be interesting how they implement it. Hell, they might be the first company to implement a story into Battle Royal. I would thoroughly enjoy that.

http://gamrconnect.vgchartz.com/thread.php?id=235742

^ Ugh, people have already stated their opinions and have started arguing about it already..

Only found a thread about Battlefield having possibly a BR mode, but didn't see that one

If this is true, I would have to guess it's because of BFV and it's rumor being true as well. Battle Royale makes way way more sense in Battlefield, mostly due to it's massive multiplayer maps. If Activision got wind that EA was having Dice add this mode into BFV, I'd have to assume with it's popularity, there's no way Activision would allow them to have an entire year to themselves over CODBOIIII.

This would also be a justifiable reason to drop the campaign for COD, or sell it as DLC later. Battlefield campaigns have never been all that great overall, so dropping it shouldn't be that big of a deal with another mode to replace it, so that's another reason Activision can use to justify dropping it from COD. Not like COD's campaigns have been that great recently either. If BFV has a campaign as well though, it would look pretty bad on COD for dropping it completely, unless the price matches the content.

I have purchased MW2, 3, BOs, BO2, BO3. Out of those I've completed the MW2 and 3 campaigns, got through about an hour or 2 of BO1 and BO2 but completed BO3 twice.

I actually enjoyed BO3 campaign because it played on stuff I'm interested in (AI basically).

I'm not a big campaign player though, I mainly play MP but to think they'd just scrap the campaign for a fad? I'd probably not buy it out of protest and let them know too.

I also think with no campaign they saved a good amount of budget, no voice acting, not loads of levels, many of which aren't converted to a MP map, no vehicle mode etc. If it's £30 then I'll bite if it has no campaign.

I would rather say that with both PUBG and Fortnite, the Battle Royale genre really exploded in popularity and both EA and Activision Blizzard wanted to cash in on that undependently. And the reason why the Singleplayer would be dropped is simply because they wouldn't have had the ressources to do both in time for the release. Besides, cutting the Singleplayer really cuts down the production budget too, with all the celebrity voice-actors not being needed anymore, so it's doubly beneficial for EA

Well beneficial financially is a no brainer if they still charge full price at launch, which is most likely, or charge for it later as DLC. While the BOIIII launch date is earlier than normal by a month, I have a really hard time believing that after 3 years of development, that a month is going to mean dropping the campaign completely. Now if your aiming to add battle royale mode, then sure, dropping the campaign makes more sense, but only if both franchises do it. If BFV has a campaign, even a short one, and BOIIII doesn't, then dropping the campaign was clearly a horribly late decision or a money grab. If it's because of a late decision, I would bet it has to do more with BFV having a battle royale mode than it does PUBG and Fortnite.

That would mean only starting working on it right now, meaning they only would have about 5 months, including creating the necessary concepts, maps, characters, character design, balancing, et cetera, and that's just too short to do it all. They must have started it some months before, probably even in last year after the release of Fortnite on consoles in September. It's quite possible that they where working on both the BR and the Storymode, only to find out one of both needed to be cut to finish the game in time, and BF V's BR announcement made for the perfect time to announce the cut on their side basically by making it look like an answer to it.

With Battle Royale having become so huge in such a short time, it sounds to me more like a bet from Activision Blizzard that they would gain more (DLC paying) players with the Battle Royale than losing for not having a story campaign or any other singleplayer mode.