I'm not entirely optimistic.
Apple finally announced what one of the worst kept secrets, a transition to ARM CPUs was. Apple is correct in its assessment that the performance-per-watt for the ARM platform has outstripped x86. Apple's A12Z is competitive with the MacBook Pro 2019 i9 in single-core benchmarks and produces a little more than half of the multicore scores with much much tighter thermal budget. It's damn impressive, but not entirely reassuring. Let's run over the facts, and Apple will be shipping new Intel Macs for the next two years. ARM Macs will not arrive until late 2020. Rosetta 2 will ship to assist running x86 binaries on Intel. iPad/iPhone Apps will run on the macOS hardware.
I have many questions and not as much optimism. ARM is kickass at a performance to watt, but Apple has absolutely nothing on Ryzen or worse the Epyc chipsets in multicore scores. ARM is amazing on a tight thermal budget, so the fact an iPad Pro is somewhat viable against the latest Core i9 MacBook Pro 2019 is impressive (even if it's roughly half as fast in multicore). I'm actually somewhat optimistic Apple in 2 years can have something semi-competitive in raw CPU horsepower on the laptop end of things (MacRumors lists a 12-core CPU). Apple SOC ARM CPUs put up big numbers on passive cooling but less so when it comes to the rest of the package. There are no freebees like PCIe controllers for Thunderbolt or a full-blown bus as a chipset is a sum of its parts and not just the CPU. AMD prints PCIe controllers on the die, and Intel requires that as part of the PCH chipset (post-Northbridge/Southbridge). This means Apple now in charge of taking on a domain that it's happily outsourced to Intel and IBM. PCIe is hardly an expression of x86 as the G5 went from PCI, PCI-X to PCIe and there are examples of ARM deployments with PCIe.
Apple’s best SOC GPU scores in Metal benchmarks 1/10th of that of AMD (currently Apple does not support a modern Nvidia chipset). Their GPUs are more than competitive against the Intel HD GPUs, but it's hardly a cause of celebration. Maybe we will see Apple shipping SOC GPU + Dedicated GPUs on laptops like they do with Intel + AMD. To make up for the shoddy Intel GPUs, on the 15-inch laptops, Apple ships with the Intel GPU for lower power and a high power dedicated GPU when watts aren't an issue. GPUs at this point are nearly as important as the CPU, considering that they end up codec mashing, machine learning, physics modeling, and so on. A great mobile GPU is not a great desktop GPU.
To circle back to PCIe is the foundation of NVMe. One of the more exciting features is that the PS4 is it's using a PCIe 4.0 SSD, which means 3.5 GB/s (not gigabits) a second. If Apple chooses to eschew PCIe, it'll mean fewer vectors for cheap storage, and likely no user-upgradable storage as m.2 has effectively replaced SATA.
Thus far, there's absolutely no information on dual booting. Thus far it is not dual bootable on the Dev kits but that's not suprirsing. Considering the amount of ARM distros and MS dipping its feet into the ARM world, it's possible but much less so, especially on Windows without standardized hardware unless Apple provides the drivers. I'm skeptical Apple really has much desire on this front.
Lastly, my fear is ARM will usher in the planned obsolesce that Apple has always dreamed of on laptops/desktops. Even today, I saw that Martin L on MacProUpgrade had already gotten Big Sur up and running on a 2009 Mac Pro using OpenCore. x86 despite its shortcomings, is rather resilient since Apple didn't create the locks to the box. I don't know what Apple will do for modular computers? I hope they do not kill them. Thinking about that makes me sad.
That said, we have probably five years until ARMeggedon, as Apple intends to sell Macs with x86 for two more years and promised "long term support" for x86, which says to me, three years of Apple support on the last x86 mac. Fingers crossed, I'm very wrong about much of this.