For myself I am most excited about Torgast. Simply because I can do it solo and just keep going still I die or get bored and hopefully I can do it more then once a day.
The thing I am least excited about is having to pick a covenent for my toons. I’m hella picky.
all the bfa rental systems being removed im the most excited for, im the least excited for new rental systems.
literally
/10char
Torghast looks really interesting. But also just new lore, new places to go to, no artifacts or azerite anymore. Yay! And the level squish too, hyped for that.
Least…I don’t really know yet. I guess that it’s still so far off.
If there’s no rental power system and everything under the sun doesn’t have a hard time gate on it and you can gain rep from sources other than WQs/dailies AND they don’t time gate flying it will be a great expansion.
I don’t have high hopes for Shadowlands…
Most excited: A Chance for them to fix their GCD decision and rip it out of the game once and for all.
Least excited: Level Squish. I don’t care about the levels. It’s an arbitrary number. 120, 130, 60… it doesn’t matter they’re always going to make the time to max level around the same regardless of the number that level is.
So how much Dev time is going to waste putting in a level squish versus putting that Dev time on things that are actually useful?
I do, may hurt me but I think they know what’s up, they know the ice is thin and they gotta knock it out the park.
The pattern since lich king has been one good, one not so good, one good, followed by another not so good. So given that pattern I’m thinking Shadowlands is going to be epic. Man I hope so, if not then someone needs to pick up the pieces and make a new home for all us wow refugess floating around in the MMO void. 
Most excited: new customization.
Least excited: the potential carryover of BfA’s design philosophy.
I really hope you’re right. I’ve never hated an expansion as much as I’ve hated BFA. I want wow to be good.
I honestly do not know much about the expansion to be excited or not excited for its release. Need to know more about what my money is going to buy me in the way of entertainment.
Yeah , same here. We shall see. But I am looking forward to new content.
Most excited for character customization and finding out more about the Covenants.
Least excited for the new rental system. I hope there isn’t one but those hopes aren’t high.
I’m looking forward to essences and azerite traits going bye-bye.
That’s funny, I’m most excited about the level squish and the changes accompanying it.
If it was just a level squish it would be pointless, but it’s not. They’re reducing leveling time a bit, and working on making the leveling experience more meaningful. There’s also the new zone scaling. As it currently stands if I hit level 85 and go to Pandaland, I get maybe 2/3rds of the way into Jade Forest before I’m 90, so being able to go all the way through an expansion on a character seems fantastic.
New systems
What do you mean by “Rental” system?
Covenants, wings (hoping that turns into a wings mount), Torghast, and cross participation chest.
Most excited: Maybe the de-pruning if they do it right.
Least excited: Covenants.
A rental system is something unique to an expansion that gets removed at the end. Legion’s rental system was having artifact weapons. The weapons are still here, but their traits are gone.
The other items you listed are a possibility, this one though I don’t ever seeing changed with the current team.