There's a few misconceptions about the MBP here. While the intel versions, if you pay up, come with the AMD RX5300 or above, its a laptop so gaming really won't be as good as a traditional desktop. It will work, but don't expect 4k 60FPS by any means.
ARM gaming is really taking off. Look at what iOS, Android, and Nintendo Switch currently offer - the games run on ARM architecture. If you look at the Xbox 360, GameCube, Nintendo DS, 3DS, PS3, etc. they all used ARM or PPC architecture - different from Intel - while having integration with, generally, AMD Chipsets. Switch has Nvidia, 3DS I believe use PICA, etc. So while you may be concerned about gaming, its up to developers to take advantage of the hardware they're given.
Let's move to the MBP. Imagine if it had dual-cpu A14X. Let's say the A14X has a 2/6 (2 efficiency core, 6 performance cores) x 2 ~ 4/12 (16 cores). Couple that with 16GB of RAM, Apple's amazing GPU - heck maybe AMD is develop a GPU to work with ARM (Samsung + AMD ->
https://www.techspot.com/news/85098-amd-samsung-rdna-based-mobile-gpu-hammers-galaxy.html) so it's not out of the question.
What about what the MBP really means - a pro workstation. Given that the A12 was beating, in raw performance, Intel's Core Series CPUs - a mobile CPU (A12) was beating out Intel Core desktop CPUs (i5) in raw performance, read that again slowly, then you're looking at one powerful machine. Couple that with all-day battery life and you're living in a dream world. A large battery that can sustain large workloads, be performant, and is capable of doing gaming - if programmers develop for it - I don't see the issue.
You won't have Windows, so what? Get a PC if you want Windows. If you want BootCamp, get a new MBP, configure it up and keep it for 3-4 years while the rest of the ARM stuff is leveling the playing field for computers.
Chromebooks, Raspberry Pis, Windows 10 on ARM (Surface Pro X) - all either have or can use some form of ARM architecture.
I hate to say it, but I think x86's days are numbered now. I give it 5 years before x86 slowly sinks to being the low-end market chipset or legacy chip. I really see ARM taking over. Unless Intel and AMD can do something to make the TDP significantly lower while increasing performance (IPC), then x86 is a sinking ship.
With all of that said, if you're wanting to hop on the ARM wagon but don't know about this first iteration, wait for Gen 2 to release. Gen 1 there will be some struggles with apps, performance, battery, etc. as the ecosystem evolves and shifts into this new era of computing.