Those seem very optimistic targets. The 40% uplift for Zen 1 was relatively easy, coming from a very poor Bulldozer architecture. It is a much higher bar to get a similar uplift over Zen 4. "Luckily" for AMD, with all the rumors and uncertainly surrounding ARL, even a more realistic 20% or so should put them comfortably in the lead in most applications.
Yes, but Zen 1 also widened the core massively, essentially "doubling up" everything and it ended up with over a 50% IPC uplift (not including SMT).
Zen 3 on the other hand managed +20% IPC while not widening the core at all. All of that on the same node with a 10% growth in size. With that perspective I would consider getting 20% more IPC from
a lot wider design to be a relatively mediocre achievement.
In the end it all depends how much silicon they throw at the problem (and how good they are at it)
Designing a core with 30-40% more IPC is very possible when the essentially double the width again (not saying they will do it, but in principle). The hard part is to not "explode" the transistor budget, keep the size and clocks in check. Otherwise it might end up like the
late Samsung cores. That were much wider than the predecessors, but also drew a ton of power and ended up no faster - while wasting a whole lot of transistors for that privilege.
Make no mistake, designing a
good 2x wider core is a
very hard problem. I'd say, it's an order of magnitude more complex task. But if it's done well, a 40% uplift is most certainly possible.
Let's not forget that nearly a decade has passed since the mid 2010'ies when Zen 1 was designed (with considerable improvements in available compute power and algorithms).
And while AMD has iterated a lot on Zen 1, they even changed many of the underlying "lego blocks" in Zen 3, they kept the overall design still surprisingly close to the original:
Zen 1
vs
Zen 4
It would only make sense to redesign the architecture fundamentally once more - to again have 2-3 generations of low-risk fine-tuning iterations (Zen 6, Zen 7 ...).
Not doing it is certainly less risky (and cheaper) but also reaps less rewards.
Just my 2 cents.