Okay.
You have my attention.

I somehow left out the The Brothers War concept art in the OP; I've updated it.

For those who want to click through, there's more about supplemental products there too, including the next un-set, Unfinity, which will be a retro space carnival setting.

Kamigawa Neon Dynasty - I am worried.
New Capenna - Art deco noir crime fantasy? Looking forward to this.
Dominaria United - Cautiously excited.
Brother's War - More excited, but more cautious.

The only one I'm not particualrily worried about them screwing up is New Capenna. No worries they'll retcon something and the original concept seems pretty neat.

Kamigawa Neon Dynasty is a very mixed bag. On the one hand, it's a very distinctly different thing than they've previously tried and it's very off the beaten path.
On the other, Mirrodin exists and I refuse to believe Neon Dynasty is inherently worse than it is.

New Capenna has me more pensive. Initially, I'm not opposed to the idea, but I am waaaay past giving a crap about Elspeth.

Dominaria will be what it is. I just hope it has a little more of the classic aesthetic rather than this vivid, overgrown approach. Just something more normal.

Brothers War has me way more intent, but I worry about what they'll actually give us. I don't think they'll do things like reprint Yotian Soldier, but we'll probably get something like Yotian Warrior that's a strictly better upgrade. But I'd rather have the former than the latter. I'm pretty damned tired of seeing strictly better upgrades and callbacks. We could see a Feldon reprint, but we'll probably get a roided out version instead. (For example)

Magic is dead

Long live Magic

What about unfinity, is it a new un-set, or just a side product containing some un cards?

I believe it's a full set