I have read through a lot of these posts... I have to say, my head is now spinning trying to figure out what the NS4 will offer, especially around the organisation of sounds
To be honest, I get the NS3 to work really great for me in a 5 piece band setting - the panels set up and especially song mode set up allows me to pre-plan songs and complexities within them really well and with my mind at rest, so I can concentrate on the performance. With a few little exceptions, where it would be occasionally nice to have an extra synth or sample layer, or such thing, I have everything I need and more and I suppose.
I feel that unless you are the core sound/player in a band, more than what we currently have on these stage instruments could actually lead to a quite mushy or muddy mix overall.
Anyway, rather than speculating about what is coming, I look forward to trying one out. For me, the big changes are the new synth and the effects.