The only legit reason I can think of for AMD to pin all their hopes on "Zen3d" or what have you until Q4 2022 or some other ridiculously late date is that AMD may be planning on committing all their 5nm wafers to Genoa + Bergamo (at least for a few quarters). While we're all paying attention to the consumer desktop side of things, what's really happening is a matchup between Genoa and Sapphire Rapids, which is a matchup Intel does not want. Sapphire Rapids will be hard-pressed to eclipse Milan, but Genoa? Not a chance. Meanwhile, us retail plebs will get the N7/N6 scraps left over.
Don't think it'll be Q4. AMD has said 2H22, but don't be surprised if they launch it earlier to trip Intel up. N6 would be Rembrandt, would it not? Extra N7 or other flavor of 7nm @ TSMC will be taken up by the IOD as there have been strong rumors and suggestions that AMD will solely rely on TSMC for the entire package including the IOD for Zen 4 and future Zens. It's going to be interesting to see how the two companies pull this off considering the shortages will last until 2023 if not midway of that year.
Your Genoa/Bergamo suggestion makes sense because they'd have a head start and have chiplets that didn't pass Epyc standards be up for binning on Ryzen products or future Threadrippers. That said, I wouldn't be surprised if AMD begins production in a few months or close to the end of the year. Or even now. The upcoming fall and winter is going to prove difficult given COVID is still rampant and the ramp down and or pause for Lunar New Year.
I'd say we'll get hardware sometime in summer if my May the 4th or 5/5 prediction falls flat on its ass.
Do we know what AMD's MCM consumer cards will utilize? As far as consoles go, there was an article posted online a few weeks back that Sony has already designed a better PS5 housing for the digital mode, and I suspect the optical disk model will get a redesign sooner or later, too. This won't affect internals much, but I suspect the refresh of these consoles including what Microsoft is offering will be offered on N6. But these will come out in 2-3 years. Enough time to not hamper production. I do not see them getting a refresh to 5nm due to costs involved of a new design. Though given the rapid improvement we may see in the near future, I wouldn't be surprised if this generation of consoles suffer from a short lifespan before the next generation is out.
April-June release goes with AMD's 12-18 month cadence. Late '22 wouldn't make sense. The V-cache is going to affect a small amount of processors per AMD's words of on the higher end of their product line. As far as I'm concerned, these are essentially XT like refreshes that have zero bearing on their cadence.
I'm not too worried about Alder Lake, Meteor Lake, Rapotor lake or their HEDT ambitions over the next few years. Let them prove themselves for a few generations with their hybrid system. Even Intel's latest mental departure involving their naming scheme has left a bad taste in people's mouths.