I've never owned a tablet but I'd say I'm 90% likely to make the Z4 my first. Nothing like starting with TOTL!
The Snapdragon 810 gives me pause due to the overheating rumors, even if they have been *mostly* debunked from what I've read. Still, I'm going to wait until it's been out for a few weeks and I've read some reviews before I make up my mind.
This has pretty much everything I want in a tablet. It's the perfect size, lightweight, has a nice aspect ratio (unlike Nexus 9) and resolution, water/dust resistant, microSD slot, 64-bit CPU, 3 GB RAM... Hopefully the battery life is good (specs indicate it will be).
My only question is whether Sony tablets are closer to stock Android than, say, Samsung TouchWiz (ick). Also I hope gaining root will be fairly easy (I assume it will since it won't be carrier-specific). I've learned some lessons from my Verizon Note 4, which remains un-rootable and I despise TouchWiz.