Nvidia changed almost nothing in the architecture with Ada, and if this continues with Blackwell, then all advancements (or the lack of them) will likely go hand in hand with node shrinks.
Ada brought huge Power and Efficiency gains over Ampere, which resulted in like 1 GHz higher clockspeeds on avg which is 50% higher. Shows how gimped 3000 series actually were and very powerlimited due to cheap Samsung 8/10nm really.
Also Ada has newer and better tensor cores, better optical flow accelerator which allows for proper Frame Gen (stutters on Ampere, even in modded DLSS FG games, simply don't work with Ampere), better RT, DLSS 3.x, Shader Execution Reordering so yeah, there is architectural improvements in Ada for sure. Many people have tried to run DLSS 3 FG on 3000 series on hacked drivers and they all failed. Nvidia is NOT doing it on purpose, as Ampere simply lacks the capability.
But sure, the biggest improvement was really Samsung 8/10nm to TSMC 4N and Blackwell is not going to get this advantage, because its 4N again, meaning chip size and/or power has to increase to gain alot of performance. GDDR7 brings some performance as well (but might drive prices up even more and Nvidia is rumoured to use only 28Gbps chips even tho GDDR7 can do 32Gbps now)
Nvidia will probably use 32-36 Gbps GDDR7 on 5000 refresh.
Most rumours so far also claim 5080 is 350-400 watts and 5090 is 550-600 watts which fits what I claim; Bigger die / More power, because node shrink won't be a thing for 5000 series. Luckily Nvidia don't really need a huge performance gain for this gen, because AMD left high-end gaming GPU market.