I think the move towards generic compute has sort of 'locked' architectures in a specific way. If we move away from generic compute perhaps we'll get absolutely whole new architectures, but at this point in time, we should be expecting evolutions in the architecture to support new features.
The core architecture is about how the GPU processes work and keeps the ALU's occupied. Terascale'sVLIW required shaders to fit a particular ideal model to maximise utilisation. GCN changed that to be more flexible. Over time, it's added schedulers and whatnot. Meanwhile, nVidia has different workloads using different functional blocks, which would have to be bolted on to a GCN design. A clean-slate design might find a better way to map workloads onto ALUs, reducing silicon complexity and improving relative performance and integrating latest features like RT and ML acceleration into the shader design, or into the chip architecture overall in the case of them having discrete blocks.
We definitely shouldn't be counting GPU architecture as 'cemented' at this point. RDNA could be a completely new design, or a GCN remaster, or a GCN remake. Incidentally, rDNA is a thing in biochem, where you inject new DNA into existing; the implication there being RDNA is GCN with stuff inserted rather than a new species altogether.
Even a 6 month lead is massive.
OG Xbox One was late to the game, which is why we saw them struggle so hard this time around. I would be curious to see how MS would respond with having 6 months less to work with.
If 6 months is enough to gain a significant architectural advantage, Sony should wait. If it's not, 6 months waiting nets MS nothing. Is it realistic that AMD had two offerings on the table, Navi 10 in 2019/2020 and a significantly better Navi 20 six months later, and Sony chose the former for the sake of six months lead sales? My guess would be that AMD had general timelines, and perhaps Sony committed to a 2019 release and got what they have, and MS decided to go with the next-gen architecture and will get what they get when it's ready, which could be anything 12+ months after Sony. The gamble being that though later, and potentially late (18+ months), MS will have a significantly stronger/more economical offering and something that's better future-proofed for their cloud ideas.
Because all things being equal, MS launching the same time as Sony without any particular advantages will just see them make the same sorts of numbers as OXB and XBO. They either need notably more power for the same price, or some sidewise USP. MS winning console market is highly unlikely, and they're all about moving people over to the XBox cross-platform ecosystem. XBox Game Pass has released on PC, for example. Design choices would thus favour their long-term goals rather than fitting the traditional console generation cycling, which would mean skipping a unified launch to have a stronger machine, conceding the console sales war to Sony and instead focussing on the best devices to slowly grow their ecosystem of more and more subscribers. Let Sony have their 100+ million consoles; MS will take the 25 million ultra-core high-end console gamers with their monster machine releasing 2021, and another 10 million from their low-end StreamBox, and all of them will start to subscribe to Live services along with others such that, by the time we're looking at PS6 coming out, MS has 100 million subscribers playing games on PC and mobile and some consoles and that income isn't going anywhere when PS6 appears.
