Unless you have a specific reason not to, my advice would be to, for the MacBook Air, 13" MacBook Pro, Mac mini, wait. The ARM based versions of these Macs are poised to blow the Intel ones out of the water, given that the A12X and A12Z in home-button-less iPad Pros already blow pretty much anything that isn't a 16" MacBook Pro or beefier Intel machine out of the water. The only exception to this is if one buying one of those Macs is doing so for testing or compatibility purposes.
For the 16" MacBook Pro, iMac Pro, and Mac Pro, I'd definitely wait. (For iMac, it's debatable and likely dependent on use) Even Apple's ARM isn't ready to overtake Intel there JUST yet. Plus most of the kinds of apps that most of the people that tend to buy those machines will need to be updated and, depending on how Mom and Pop your software vendor is, that may be a bit of a wait. I know we saw Maya running in Rosetta 2 smoothly, but I still wouldn't gamble. By the time you kick yourself for not having an ARM based 16" MacBook Pro, an Intel MacBook Pro will be middle aged anyway.
As for your assertion about Mac OS X Leopard, it was supported and the latest OS until August 2009. Even PAST that point, it got security patches until 2011. If you bought a PowerBook G4 at the last possible moment in 2006, that is still five years of life, which for back then, was considered impressive.
Gaming on Mac sucks. The Retina display made that ****** (because most GPUs couldn't keep up until very recently), and then Catalina killing 32-bit app support basically wiped out 75% of what was left of Mac gaming. Or at least PC titles on Mac. If you want to play PC titles, just get a PC to do that. A $1500 Mac, even one with Boot Camp, isn't going to be as good as as $1000 PC at playing games.
That said, even if Windows 10 on ARM64 becomes doable via virtualization or a new Boot Camp assistant or both, Windows 10 on ARM will only run 64-bit ARM, 32-bit ARM, or 32-bit x86 apps. 64-bit x86 (known by Microsoft as x64) apps won't work. That's not to say that you are not still left with a good deal of x86 compatibility there, but if you're gaming with games for Windows that are 64-bit x86, you're gonna be **** out of luck on an ARM Mac. In which case, I might get an Intel 16" MacBook Pro now (or at least before they're replaced with ARM version).