USUM seems like it's going to be a pretty good update for PU, with many Pokemon getting tools that don't break the tier but help them become more viable or splashable, in that sense it also helps in making the tier less centralized on some Defog / Stealth Rock users now that we might have more options available. Don't like theorymoning that much since we can't exactly predict how the metagame is going to shape up, something might rise or drop from the higher tiers and change everything, but personally I'm hyped for some things.
Palossand getting Stealth Rocks, this could be either huge or not that much, since I'm not sure how Palossand could fare off against some threats without either Toxic or one of its stabs, but we'll see. I'm probably more inclined in running both the stabs, I feel like ground ghost coverage might be something too good to pass out on, but it depends on your team's preferences I guess. That said, compressing the role of Stealth Rock setter, Fight answer and spin blocker in one slot is very good from my standpoint, and role compressors are what PU is looking for right now, so I definitely think this could get some use, will try to do something with it.
People already talked about Lurantis, but I wanted to add something. Lurantis is of course going to be better with the addition of Superpower, and I think you could actually go for a more offensive set and run Knock Off in addition to Superpower and Leaf Blade. Knock Off is actually so good on this, since it allows it to make Oricorio not a guaranteed switchin anymore, and greatly helps pressuring phys walls such as Weezing, which was said to be one of the best switchins this has. Also its base attack stat is very solid and gives it the kind of immediate power that an offensive set needs. That said I don't think this will get that much better since its typing and speed are still dong, but these are good additions for sure.
This thing Choice Banded is already scary as fuck as it is now, and it will be even more scarier after it gets Knock Off and the other coverage options. Knock Off is the biggest buff it could've gotten both from a breaker point of view but can also get it a bit more usage as a revengekiller I feel like. You can easily kill off a weakened foe with it or something that gets hit super effectively and if the opp wants to preserve it he has to potentially lose an item on another mon. I don't think CB variant of this actually has any safe switchin that doesn't get worn out. jklioe already talked about this, on the Choice Band set in particular, and I feel like he was pretty informative so check his post out. Will definitely toy with this a bit though huehuehue.
People might be undervaluing this form a little bit. While the other does some roles better I found Lycanroc-Midnight quite good as a revengekiller with the Choice Scarf. No Guard makes Stone Edge completely safe to use, which hugely helps with rkilling stuff, along with 115 base Atk that allows it to run a +Speed nature and still hit hard. Right now I have to use stuff such as Return and Brick Break to fill in the last two slots, but the addition of useful coverage moves in Zen Headbutt, Iron Head, and Stomping Tantrum finally allow this form to express its revengekilling potential a bit better, even though there's still very little reasons to use it over Primeape or Passimian potentially.
Another minor thing, Dpulse on Eggy alola is good but nothing extrardinaire, you still want to run Leaf Storm if you run Dragon Pulse to not lose out on much power, it's just an additional combination you can go for even though I still like Z Meteor + Giga Drain best.
Defog users I'm looking forward mainly are Altaria and Volbeat. Altaria can become viable because it can check some special attackers such as Magmortar, has a reliable recovery, and that along with Natural Cure might make it a longlasting hazard remover. Volbeat I feel will be more of a gimmicky Defogger but I can see it working because of Prankster, being able to annoy fight types, and other tools such as U-Turn and Twave that give it further utility outside of Defog.