Simply quadrupling the die isn't really feasible, the price increases exponentially.
Even if the SOC was $500 cost price they would still have plenty of room to pay for everything else and hit the $5k price point.
I mean, they could even use separate highly integrated chips to get that number of cores too, although I suspect they will want to do it on a single chip assuming cooling is OK.
What you're talking about at the end is chiplets and it takes a lot of work to get it to operate, just ask AMD.
I guess the question is, to what end?
- Apple hasn't had a good history with B2B sales. Evidenced by them getting out of the server business.
- Apple doesn't want to be a cloud infra company. Evidenced by them using other cloud providers to host iCloud.
- Maybe, Apple will one day sell servers again, or sell M1-like chips to cloud providers. However, we have no evidence of this. Apple prefers B2C products with 5-6 year refresh cycles. Their superpower is vertical integration rather than selling a single component.
- Cloudtops are becoming more and more popular, in-tandem with a powerful-enough laptop to appropriately hold local state such that the UX is responsive. Large companies that do software development, ML training, VFX, etc are already using cloudtops.
That said, small companies and individuals haven't yet started using cloudtops for intellectual property creation and a Mac Pro could still help their workflows.
With that in mind, where does Apple grow this high performance market? If there is no future for this market, why invest into any R&D? Let the Windows ecosystem continue to handle it for the few years it still exists.
Meanwhile, to help those small companies and individuals improve their current workflows, maybe Apple will release one or two more Mac Pros, but more likely than not all Mac Pro development will stop. I'm likely wrong about all of this but I feel, Apple will instead offer a "seamless compute cloud". Similar to their strategy with https://developer.apple.com/xcode-cloud/ they will likely release a general purpose service for "cloud cores" i.e. the machine will locally have 6 high-performance cores, 2 high-efficiency cores, and ∞ remote-performance cores that are seamlessly integrated and run Apple's Universal Binary in "their cloud" (likely through AWS/Azure/GCP). Then no matter what the workflow is (e.g. photo/video/audio/game editing) you get a local preview (e.g. a low-res render locally) but in parallel the final product is built remotely and the data mirrored back to your local machine.
The only other reasons to keep building beefy machines like Mac Pro are for iCar Self Driving or to sell "cloudtops" (as I described in the paragraph earlier) but in a B2C context, i.e. the cloudtop runs in your local LAN/WAN or even as your home's Wifi router to reduce latency and accelerate all the Apple devices on the network. However, its not clear if they will invest in the software first or the hardware first for this distributed compute future.
What's the alternative? That they release another Mac Pro with intel, despite their stated intention to move everything away from x86, or that they release a Mac Pro with just a laptop chip inside?
Let's remember that Apple has an annual R&D budget of c$20 billion, so it won't be totally shocking if they diverted a small fraction of that to build out a desktop processor.