It's probably not what you think. Assuming that they shrinking down the GPU die to 5nm EUV, I imagine that will be enough on it's own to deliver a decent performance improvement without requiring huge amounts of power (in combination with other optimizations). AMD has confirmed they are increasing the power reqs. for RDNA 3, so I would expect a max power consumption of between 350w-400w for the top GPU die, so they will need an improved cooling solution (considering that hotspot temps on the 6900 XT were ~95°C).We will find out just how good AMD's chiplets are, Lisa Su confirmed RDNA 3 uses chiplets
That would in theory allow RDNA3 to achieve an overall performance improvement of >50% vs RNDA2. But probably +50% improvement at 300w for the GPU die below the top tier.