I have to somehow make a correction to your post

The Nord Piano 5 imho does, apart from the double sample synth storage 1GB vs 0.5GB and the keybed, not have any monstrous advantage over the Nord Stage 3.
Nord Stage 3 already has 2 layers of each sound, if they continue tradition and release a 3 EX, it will most likely only receive more Piano storage - more sample storage would be a first!

I really can’t wrap my head around what they might do with Electro 7, though ... the new features of the Piano 5 really surprised me

As it is now:
Electro 6 - per Program
1 Organ ... 1 Model, 2 Drawbar settings
1 Piano ... 1 Nord Piano Sample
1 Sample Synth ... 1 Sample
Piano 5
2 Pianos... 2 Nord Piano Samples
2 Sample Synths ... 2 Samples
Stage 3
2 Separate “Panels” of a set of the 3 engines, resulting in
2 Organs ... 2 Models and/or 2 Drawbar settings
2 Pianos ... 2 Nord Piano Samples
2 Full Synths or Samples ... either a Synth engine or Sample, each can be tweaked with a filter, mod env, LFO,...
I think I’m going to include a comparison list of the different Nord Models in my Wish List
