Okay! A lot to unpack here.
Software totally aside, I'm unsure as to the operating condition of your 2012 MacBook Pro with retina. This might be the real determining factor as to the matter of WHEN you are to replace this Mac.
As for software, you're able to run macOS Catalina, which will still receive security updates for the next two years. If you've got 32-bit apps that you're not keen to let go of (and trust me, you're not alone there), then macOS Mojave is also an option for the next year before it stops receiving security updates. Catalina should still support most applications for the next year though, and staying on it isn't a bad way to ride out waiting for an Apple Silicon Mac if that's what you want to do.
As for the 16" MacBook Pro, I'm not sure what about the screen is less than satisfactory to you, especially when compared to the 2020 13" MacBook Pros (not a typical comparison to be making in the latter's favor at all). The webcams still suck on all of the currently shipping MacBook Pros and Airs, but the displays are pretty decent, all things considered.
Intel Macs are very likely not going to get dropped any quicker than they otherwise would've if Apple hadn't decided to make this switch. Your 2012 Retina MacBook Pro is only losing support now. That's eight years of being supported for the latest release and two thereafter of security update support for the newest release. The amount of time the average Mac lasts before it is obsolete in terms of software support from Apple has been steadily increasing over the past decade. The first Intel Macs only had five and a half years of support for the latest OS and then two thereafter for security updates. This isn't an Intel vs. PowerPC thing, this is just how Apple is supporting their Macs. If you bought a 16" MacBook Pro today it would likely be supported for at least the amount of time that you've owned that 2012 Retina, easily.
The question of whether or not you want a Mac with Intel or a Mac with Apple Silicon depends on many other factors. If you value Boot Camp or dual-booting/virtualizing other x86 operating systems (such as macOS Catalina, x86 versions of Windows 10, or x86 versions of Linux, or older macOS releases via virtualization), I'd get an Intel Mac. If those things don't matter to you, then I'd try to hold out. Incidentally, buying an Intel Mac now and then buying an Apple Silicon Mac after they've had more time to mature following the end of this transition isn't a bad way to do it either. So, in short, if you want that 2020 13" MacBook Pro (because you, for whatever reason, don't like the 16" MacBook Pro), get it! Though, given that it's heavily rumored to be the first machine to make the jump this year, I might wait. But, again, that's all dependent on how you feel about the move to Apple Silicon. While Apple is handling this transition very similarly to how it handled the move TO Intel, the implications of this transition are very different from that previous one.
Lastly, should you leave Apple? Assuming you're solely talking about whether or not you should leave the Mac platform (as you can totally function just fine with Apple's other platforms and Windows instead of macOS), I wouldn't base that off of Apple's hardware offerings. They are what they are. And right now, with the butterfly disaster fixed, and the 16" model actually having a decent thermal architecture, I'd say that from here on in, the MacBook Pros are gonna be just fine! I'd make your determination as to whether or not to leave the Mac platform solely on how you're feeling about macOS and not the hardware on which it runs. Apple's quality control with macOS has suffered in recent years. It seems like some of that may be fixed by Big Sur's porting and re-engineering of the stock macOS apps from their iOS counterparts. Certainly, that won't fix everything. Apple still releases new versions of macOS too quickly and many of them suck for that reason. How you feel about that, how you feel about using a Mac versus Windows or Linux. And what apps you even use a Mac for should dictate whether or not you stick with the platform.
For what it's worth, I'm at a similar cross-roads, I'm very likely picking up a 2020 13" MacBook Pro (I have PCs that can better do all of the things that I would've otherwise done on a 16" MacBook Pro, though it is still very tempting) and because I still make use of x86 based dual-booting and virtualization. Plus, I know that, even after whatever Intel Mac I buy stops getting security updates for macOS, I'll still have Windows 10 support for many more years to come (case in point, Ivy Bridge Macs such as yours STILL work in Windows 10 and will continue to for quite a bit of time longer). But beyond that, my needs for a Mac are minimal. I've had my foot out the door from the Mac platform for years now (and it's much worse now that Catalina killed support for all of my 32-bit games and apps). I might take a Final Cut Pro class for ***** and giggles, but past that, I sort of don't need to be a Mac person anymore. If you find that to be the same for you, again, that's a software thing, not a hardware thing. But if that's the case for you, then the debate over whether or not to buy a Mac now or later was a moot one to be had anyway.
Hope that helps!
