The new Arcam cabinet design looks fine to me, but the finish doesn’t compare to what would be an Ultima3 level. Just judging by net product weight, I suspect the Salon2 cabinet is much better braced, and the Arcam cabinet would need improved, as you suggested.
Also, the Salon2 was “just” discontinued in 2023, and it still is one incredible speaker. There’s a thread on ASR questioning if the Salon2 is still state of the art. In my mind, yes, it is. Unless they want to do an external active crossover, I don’t know what else they can do? Improve the waveguide a bit? Sure. Maybe improved drivers? Maybe. I say “maybe”, because new marketing buzz words and acronyms aren’t improvements unless confirmed by measurements.