Maybe someone already posted this, sorry don't have the time to go through this many pages... but anyway... there are some recognizable faces in the poster DiTerlizzi posted.
The Lady of Pain in the middle, of course needs no introduction. She sure trimmed down her collar of blades to just a half-circle though.
Behind her are two Dabus, the enigmatic caretakers of Sigil and the extension of her will, who speak by hovering symbols. Also, a Mercane (Arcane), the plane-hopping giant blue merchants whom 5E already re-introduced in Spelljammer, and some Monodrones.

The cat eared/tailed lady on the left corner peering behind a doorway is the Cat Lord, the anthropomorphic representation of all felines in the multiverse, from the Beastlands. While almost god-like in nature they are not real deities nor ask for worship, so I guess technically they could get into Sigil.

The Githyanki knight next to her is bazed on Kharzed, who appears in the Monstrous Manual Planescape Appendix I.
To the right of him is a Green Slaad, in a mix of DiTerlizzi and 5E style, though notably having the ruby gem in its forehead that can be used to summon them. Maybe this could be Xanxost, the famous fiend-expert?

The Human girl next to the Slaad is based on the art for a generic Outsider, aka people who just arrived to Sigil and are clueless about the multiverse, and she looks just as hopelessly lost as she did in 2E.

On the far right in the doorway, looking smug and recognizable for all the ioun stones around him is Xaositect lawyer Sly Nye, a Tiefling. He seems to have grown a nose in all this time.

The Mephit in the foreground on the right could just be a regular Dust Mephit, but could also be Seamusxanthuszenus, the proprietor of Parts and Pieces, a shop selling planar animal parts as ingredients for spells and other purposes, no questions asked.

On the right in front of Sly is defintely a Rogue Quadrone, it could be a new character of course, or maybe it is Ylem who tries to introduce a little chaos into law and create a sentient form of Spellhaunts.

The Dwarf-like guy in the spiky helmet seems to be based on the Bedlam guards, which is a Gate-Town to Pandemonium, no idea what would they be doing in Sigil.

The blue-skinned Tiefling lady next to the Quadrone seems to be based on this drawing, and based on her tattoo, she is a Doomguard.
You can also see the Sensate logo on a flag, and on the left, the sign of The Friendly Fiend shop, Akin the Arcanaloth's store.
And the floating skull (in a hat) could be a Mimir (like Morte), but the gems for eyes kinda make me think it is a Demilich.
That is potentially problematic though. I didn't touch Planescape in part because of Tony's art.
But, umm, why? His art is what made Planescape iconic. It has given it its unique style.
Don't tell me DiTerlizzi too has been cancelled because someone dug up something he said 20 years ago. Can we just give this nonsense a rest, before everyone in existence is banned? Don't tell me you never said or wrote anything online you regretted in a moment of anger or confusion.
I also want to see the Guardinals, Celestial Eladrin (Arvandorei? Sidhe? Azatas? whatever they're calling them now) and Rilmani back in 5e.
5E has brought back pretty much all the classic Demons, Devils and Yugoloths by now (except the Piscoloth for some reason) but it remains ridiculously light on the Celestial side. We have 1 type of Deva only, the Solar and Planetar and that's that.
I wish we got the (2-3E) Archons back, Guardinals, and yes, maybe rename the old 2-3E Eladrin something else, but bring them back.
I'd love to see Formians too, and yes, Rilmani. Plus, they should finally give us stats and artwork for the Hierarch Modrons... so we can have minis of them. As a side note, I am really hoping Wizkids makes a Modron Warband mini set for those of us who wanna recreate the Great Modron March.
Oh, and make the setting an actual setting, not a pathetic grab bag of rules designed to run one specific and inadequate adventure. And bump the damn page count up a LOT from Spelljammer, for pete's sake. Dump the GM screen to do it, if its not already too late.
Spelljammer suffered from how it had to spend about 2/3 of the lore book on introducing Wildspace and speljamming, and then tons of pages on the various ship descriptions and stats alone. Planescape has no unique mechanics outside of the gates, so I am hoping that instead they can spend this space on the various planes plus Sigil itself.
Alignment- Planescape uses alignment, 5E does not...... It would seem like they would 5E wash the planes into "sort of good" and "sort of evil" places? And that would not really fit with the setting. I would like to see the old 2E alignments, but doubt they will even consider that.
Where did you get that from? 5E still has alignment for specific characters, and all extraplanar creatures tied to planes like Slaadi or Modrons are "always XY alignment". Only regular humanoids are described as "any alignment". Even Dragons have "usually XY alignment" in Fizban's.
The alignment system still exists, they just made it more free for various races to be any alignment in games.
As well, some cool NPCs like Shemeshka the Marauder, the Us, and Alluvius Ruskin would be awesome to see, hopefully with stat blocks to accompany them!
I expect Shemeshka will show up, probably as a narrator. She appeared in Mordenkainen's Tome of Foes where it was supposedly she who influenced Bigby to share his friends' writings with the world.
I would really love if they give useful directions for those that want to play before the Faction Wars. Full rules for all the 15 Sigyl ruling factions before the war.
I know many people like the Faction Wars and it is all ok. But lots of us (including myself) consider it what broke the setting.
Couldn't they just undo the whole thing? As far as I know, 3E/4E never referenced Planescape in any large detail other than a few Dragon magazine entries. The last adventure that really mattered at the end of 2E was Die Vecna Die, and the factions still existed back then. We could make that the end of 2E and just erase the stupid Faction War from canon. They certainly have erased things from settings already in 5E before.