Like some have already pointed out, the problem with the single IP factory approach is that they only have 4 studios making games and only one of them is not a factory (for now). It's just dumb, even if Microsoft gets to keep the IP. You can't rely so much on outsourcing because what the fuck are you going to do when one of these second parties land a hit and then decide they want to go do something else, work on their own IP or whatever it is? You just can't build and nurture new IP with that mentality. It's stupid and incredibly short-sighted for any platform holder, unless you have a monopoly like Valve.
Imagine the very hypothetical and insanely unlikely scenario where Scalebound is a hit and becomes their new Fable. In the event that Kamiya moved on, who the FUCK would replace him? Talent in the AA/AAA space is becoming more scarce every day, so when you find that talent you better grab them and make sure they are happy working for you so they won't leave. That's what they should have done with Bioware when they had the chance. Or Double Helix. Both were snatched up under Microsoft's nose. They can't, or don't want to take a long term approach. And that's bad. It shows a lack of commitment to this business.
Once you have a nice stable of talented studios, you brand becomes strong and the case for people to buy your box will make itself. This is the age of social media where perception and opinions spread like wildfire. But what have they been doing? Mismanaging and shutting down what little studios they had. Rare, Bungie, FASA, Ensemble, Lionhead, Press Play. Consumers aren't that stupid, they will compare you to the competition and be vocal about it.
If Microsoft understood studio/IP building, today they could have more than 10 good studios alternating between a tentpole IP and something else every 2 or 3 years. Don't even need 2 full teams for that, have a small team to prototype the next thing while the current project is finished.
Take 343i for example. Put them on steady a cycle of Halo and something else, something smaller. Could be Perfect Dark, which doesn't have a huge scale and is a genre they're more than familiar with. Example:
2015: Halo 5
2017: Perfect Dark One (Remake/reimagining of original)
2020: Halo 6
2022: Perfect Dark 2
2024: Halo 7
Not only does their output look much more attractive for gamers, it also gives more time for Halo to recover from franchise fatigue. I know, Halo is a staple, but if they don't give it time to rest the cashcow will undoubtly dry up sooner rather than later and they'll end up ruining their biggest IP. Sales are already declining. This doesn't need to get in the way of how 343i operates, they can keep the staff that has no input in the games working on Halo merch or whatever for eternity if they want to.
This is what we currently expect from 343i:
2015: Halo 5
2017: Halo 3 Remake
2018: Halo 6
2020: Halo Reach 2/ODST 2?
2021: Halo 7
Good luck attracting new consumers with that.
Look at how Rockstar or Bethesda treat their biggest IP. They give them time. Or even fucking EA with Bioware. 5 years without a new Mass Effect. That's perfect, people are starving for it. That results in more interest, more units sold, and overall a stronger, healthier IP.
Microsoft could have today:
343i or Bungie on Halo + Perfect Dark/New IP
Rare on Sea of Thieves + Banjo/New IP.
Black Tusk on Gears + Jet Force/New IP.
Turn 10 on just Motorsport.
Playground on Horizon + PGR/Kart racer/Rallisport/Midtown Madness
Double Helix or Iron Galaxy on KI + Battletoads/New IP
Twisted Pixel on Conker + SplosionMan/New IP.
Press Play on New IP + Max/Voodoo Vince.
FASA on Crimson Skies/New IP + Mech series/New IP.
Ensemble on Halo Wars + Age of Empires/Rise of Nations.
Lionhead on Fable + New IP, or if they were smart in the first place, Bioware on Mass Effect + Dragon Age instead.
Undead Labs on just State of Decay.
Moon Studios on Ori + New IP.
"Bu bu bu most of these studios weren't very profitable". Fuck off, you're Microsoft. You don't become a global leader in a day and by playing it safe. Grow a pair and compete.
TL;DR: Fuck Phil Spencer.