Soviet tank development in the 1980s seems to have split along two avenues. The first was modest upgrades to the T-72 and T-80 lines, which produced the T-72BU (T-80 fire control, new engine, renamed T-90 post-fall) and Object 292 (T-80 with a 152mm gun). The second were more radical tank designs that were nonetheless still based on T-72/80 architecture, namely Object 187 and the Black Eagle project, both of which had the intent to rectify deficiencies in the T-72/80 lines. The most notable features were new welded turrets and expanded hulls that offered better protection and ergonomics, as well as better ammunition safety.
What I suspect is most likely to happen is continued development of the Black Eagle design on the high end as a T-80 successor, and the T-72BU adopted as the low-end, with Object 187 and Black Eagle features steadily retrofitted on as time goes by.
As such, I don't think an Armata equivalent would be around at this point. Apparently tech developed for the Black Eagle was applied to the Armata, which suggests to me the Soviets are still going to be improving that tank even in the 2020s.
An M1 successor, meanwhile, is highly likely. While the M1 would still be a good match for the T-72, T-80, and likely even the T-72BU, I do think the Black Eagle would have been fitted with the 152mm gun and that would have prompted a panicked reaction from NATO.
Oddly enough, that isn't exactly the case. The M1 design is
surprisingly future-proof. Especially since they fitted 140mm guns on the damn thing for testing.
What would probably happen would be the US's ETC project would have been forced forward, leading to the first ETC guns numerous decades early (between peace dividends and the data getting
wonky during testing of ETC propellants, the program was scrapped). Remember, the US had an ETC project during the late Cold War and was originally started to replace Phalanx CIWS systems (the prototype was a guided 60mm revolving autocannon system). The US Army part of the program was toying with 120mm and 140mm ETC guns (the M1 that was used to work with the 140mm gun was called 'Thumper'). At the velocities that ETC guns can generate (~2-4km/s), DU would be practically useless (the biggest reason that the US uses 'short barreled' guns is that DU has this
very useful property of self-sharpening with a side order of
setting everything on fire but at the cost of velocity as 1.55km/s is the 'acceptable' velocity for the self-sharpening property) in comparison to tungsten.
So, we'll be seeing M1s with a more efficient turbine (the M1 hasn't gotten its original turbine design replaced in
decades, which is why it's considered a gas guzzler, although the APU that was
supposed to be fitted onto the M1 got added on in one of the early upgrade packages because Congress thought having one was too expensive at the time).
Eventually you would likely get something that
looks like a bog-standard M1 on the outside, but under the hood, it's a whole other beast.
