Xbox Series X, as per a recent statement from Ubisoft. Assassins' Creed Valhalla was announced by Ubisoft on 29th April on a live stream where artist BossLogic designed the game's artwork.
After taking a hiatus from releasing shorter and smaller than Odyssey, which received a lot of community backlash for being too grindy.
In a recent statement to the Portugal branch of Eurogamer, Ubisoft revealed that the game will get at least 30 FPS on the Xbox Series X. However, Ubisoft states that the game will still benefit from faster load times and improved graphics because of the Xbox Series X's next-generation hardware. It seems like the game will feature load screens as well, and not deliver a seamless experience which many next-gen games are promising to deliver, banking on the SSDs of next-gen consoles. Since this is about the current state of the game, the developers might be able to optimize it by the time it is launched.
Considering the hardware inside the Xbox Series X and the graphical advancements in next-gen games, 4K 60 fps might be a bit far fetched. Microsoft's claim of 60 FPS being the standard didn't mention the resolution, so it is likely for 1080p, which Assassins Creed Valhalla should be able to manage. The RTX 2080 Super, which should roughly be the benchmark for the Xbox Series X, fails to hit the 60FPS mark on average in Assassins Creed Odyssey as well as Assassins Creed Origins at 4K resolution.
While 4K 60 FPS is a high benchmark and could instantly swing consumer favor for a console, it's also likely that not every game will be able to manage to reach that, especially early on. Current GPU technology that can hit that high benchmark costs about twice the speculated price of the Xbox Series X, so it's unrealistic to expect that level of performance for every title. However, games can sacrifice a bit of visual fidelity to achieve better performance. As the Xbox Series X release date creeps up on consumers, however, Ubisoft has only a little time remaining before Assassin's Creed Valhalla's Xbox Series X optimization becomes locked in place.
Source: Eurogamer