Of course publishers will still show adverts...but if your main source of revenue drops 50% overnight - that's going to be a huge problem for a number of content creators...which is what Facebook are warning against.
Most of FB's revenue is direct inventory sold - so this won't be too much of an impact on their owned and operated inventory - but as I say, it's publishers who rely on Facebook's targeting to generate high eCPMs to efficiently monetize their audience that will suffer most.
File this under actions by a megacorp that increase the power of them and other megacorps.
In the short term I expect companies like Liveramp (which acts as DMP (Data Management Platform)) to get more business because one theory here is all free apps will start to force users to login (using email/mobile number) which effectively becomes another ID you can track folks with across-apps over time.
I don't want to be stalked online, and I'll raise a glass over their bankruptcy notices.
Also, forcing users to login may also be in breach of GDPR, if you don't have a good reason to need a login, you're unnecessarily collecting personal information.
One obvious example of this is NVidia, you've paid for the card, yet they force you to login to use their apps.
One thing I am curious to see (how it pans out) is if device fingerprinting (IP + Device+ Some other attributes etc. to map you) evolves to solve this problem.
In my experience, it is pretty bad (at best 30% compared to IDFA/Device Id solutions) but I see few companies pitching this as an alternative.
Nail. Head. You hit it.
Those apps will still show adverts, publishers will still get paid, and advertisers will still pay to show ads. The only thing that needs to change is the way Facebook choose which adverts to show. Instead of an algorithm based on huge swathes of personal data that they've tracked it'll need to be a simpler "what categories of ads should we show in this app?" form. Adverts will be a bit less effective, which could drive revenues down a bit, but the sky is not falling on the ad model.
The real thing that Facebook are sad about is the fact that they will no longer be able to sell access to the tracking data. That's a lucrative business, and it's one that only really benefits Facebook and data brokers. Cutting off their supply of tracking data isn't a bad thing.