Anyway, the thread was "what would you like to be surprised by".  If they did that, and I am not saying they are, I would like to be surprised by that.  I make no predictions, merely that it would be a nice surprise IF they did that.  Well, it would be a nice surprise to me.
Yes, realism isn’t required here! Though for me a rebalancing of the game in favour of a party of six 
wouldn’t be a welcome surprise. I’d probably want to be forewarned so that I could have some time to reconcile myself to a change like this 

.
Ah, if realism isn't required, I didn't get the memo. Sometimes I default into the "Pour cold water over it in the name of realism" guy. If realism is no big deal, here's my surprise wishes: 
-D/N cycle 
-Massive world to explore, complete with many dungeons, detailed towns, wide wildernesses, and interesting characters. 
-More BG2 characters returning, including Edwin the Lich, Jon Irenicus (specifically whatever monstrosity remains of him), Viconia (original VA), Jan Jansen, etc. 
-BG2-level companion quantity (like 15), with Dragon Age/Mass Effect level quality/depth, and current BG3 levels of permutations for interaction. 
-Being able to use any spell, ability, or move on any character or environment and have it produce a unique response in some way. 
-
 Somewhat joking, but the Dead Three decide to put some of their Divine Essence into the tadpoles as a means of weaponizing the Cult of the Absolute to its greatest capacity, but something goes wrong and we end up with the consciousness of the Bhaalspawn. As a result, somehow Sarevok returned.
-Z axis tilting and the ability to keep the camera zoomed in. 
-Interactions with deities and patrons. 
-Significant shades of grey in moral decision-making and the ability to have different flavors of neutral and evil.