Some theories on possible Ascendance monsters/monster related stuff:
These aren't hopes of mine (as a matter of fact i dread one of them), it's just, stuff i could see happen.
*PSA: If you see this in the future, do NOT tell me about any of these being confirmed or denied, i will learn it by myself when i choose to.
Guardian Apexes
Reasoning: Flagship/ Important marketing monsters tend to get variations in the additional content, the new gimmick monster type is constructs, and Arkveld already has a guardian variation. Furthermore, there's something odd about Jin Dahaad that seems to tie it to guardians somehow, with its gatekeeper status and black eyes.
More flagship returns
Reasoning: I'm fairly certain we're due for Fanged Wyverns for armor set boosts, if you catch my drift.
More flagship guardians
Reasoning: Some of them are elemental monsters + good marketing if one shows up in a trailer.
Azure and Sakura Raths, Purple Gypceros, Shrouded Nerscylla, Blue Yian Kut Ku, Emerald Congalala, Copper Blangonga
Reasoning: Normally high rank versions of their respective main species introduced in expansions. In Wilds most don't appear before high rank, so, would make sense for them to be master rank variations instead.
Note that some seem more likely than others, namely those with unique gameplay elements compared to their regular counterpart.
Khezu
Reasoning: I think Shrouded Nerscylla is likely to make an appearance.
Rajang returning alongside Kirin
Reasoning: Rajang's absence in Wilds despite several other ape Beasts being here seems to me like they are waiting for its favorite prey to make an appearance, as they should (looking at you, Rise).
More large scale monsters never previously seen in newgen
Reasoning: Gogmazios was 4U exclusive, Lao Shan Lung is also returning. It seems they are actively trying to pick a few spectacle-heavy monsters.
More Amphibians
Reasoning: So far the only one we got is Chatacabra, and we could use more to make use of the new monster type armor set gimmick.
More semi-aquatic monsters
Reasoning: Underwater fighting is currently only used for Lagiacrus. It is unlikely that they would have gone though the trouble of making underwater combat return to some degree only for one monster.
Black Dragons could be a plot point postgame
Reasoning: If the expansion is about Elder Dragons, the logical climax would be encounters with Black Dragons. This isn't even to mention that Wilds's story had already evoked not just Fatalis through Zoh Shia, but also, and, more oddly, Erik briefly references Dire Miralis while trying to make sense of the Scarlet Forest's namesake waters.
Looking at my previous point, i'm just sayin'. (<- this is a joke, mostly)
Zoh Shia will stay relevant to the story, and will get an arch tempered event quest in master rank
Reasoning: Zoh Shia's perpetual healing was built up post-game, with a second fight being canon to the story timeline, yet it did not get an arch tempered fight.
Valstrax (Ew)
Reasoning: New Locale fits Valstrax's preferred high altitude habitat, it's a flagship, and people have no taste so it was very high on the 20th anniversary monster popularity poll.
If it turns out to be here, i hope it can be framed in a less serious way story and music-wise, and with more distinct weaknesses: Valstrax could genuinely benefit from being taken down a few good pegs, and embracing the fact that its design is ridiculous, to prevent it from having "most important monster ever" syndrome like it did in GenU and Rise. Also fixed wing fingers anatomy that doesn't involve its bones being broken in impossible ways would be a must.
Ascendance flagship is an Elder Dragon?
Reasoning: Story was mentioned to be about Elder Dragons. Also Having an elder as the expansion flagship has been kind of a pattern since GenU.
I'm personally neutral on that, i just hope whatever it is it's uh, not as boring as Kushala and Vehlkana yet not as borderline spinoff-y as Valstrax, Magnamano, and Arkveld.
Yama Tsukami? Nakarkos?
Reasoning: Following the logic of the previous point about large spectacle monsters, and the existence of the new Cephalopod monster type, it seems possible to see one of those monsters return, albeit no longer as an Elder Dragon.
Yama Tsukami Is present in MHStories 3, which was also hinting at Lao Shan Lung's return, so it seems more likely to return than Nakarkos.
Old world Bazelgeuse?
Reasoning: Unlike most new world monsters, canonically (from MH:Iceborne dialogue), Bazelgeuse was initially discovered in the old world, but was too rare to be properly studied, though it is known to be noticeably different from its new world counterpart.
Non-Construct new world monsters?
Reasoning: This one is a big stretch and solely based on my confusion over why Anjanath features so heavily on MHWilds merch.
