In brief: As one of the biggest game publishers in the world, Ubisoft has seen fit to dedicate an entire support article to discussing its plans for the next generation of console gaming. These plans include information on next-gen cross-play, cross-progression (cross saves), and, of course, backward compatibility.
We'll discuss each of these plans in turn, starting with cross-progression. Cross-progression essentially refers to any games that will let you retain or other game progress even after switching between consoles.
There are two main categories here: games that only preserve saves when switching between consoles of the same family (for example, from a PS4 to a PS5) and titles that let you switch between brands at will.
Both lists are relatively short, but the former currently only consists of two games: Watch Dogs: Legion and Rainbow Six Siege. With both of these games, progression will only be transferable within your console's brand.
As for the latter, Assassin's Creed Valhalla, Immortals Fenyx Rising, Riders Republic, and Hyper Scape are all included. This means you can swap between console families at will while keeping your saves intact. For most of those games, support for PC and Stadia is also available.
Unfortunately, for all of the games mentioned above, any "hard currency" (presumably premium currency) you've acquired in-game cannot be transferred between console brands.
The next set of games Ubisoft lists in its support article include titles that are eligible for a next-gen upgrade at no cost. So, if you buy a game on PS4 or Xbox One, you can get a free upgraded version on the PS5 and XSX.
This list includes Watch Dogs: Legion, Assassin's Creed Valhalla, Immortals Fenyx Rising, Riders Republic, and Rainbow Six Siege.
Backward compatibility is where things get a bit dicey. As expected, all of Ubisoft's Xbox One games will be fully backward compatible with the Xbox Series X/S, but PlayStation 5 users aren't so lucky. The following PlayStation 4 titles will not be playable on next-gen:
- Assassin's Creed Syndicate
- Assassin's Creed Chronicles Trilogy Pack
- Assassin's Creed Chronicles India
- Assassin's Creed Chronicles China
- Assassin's Creed Chronicles Russia
- Star Trek Bridge Crew
- Werewolves Within
- Space Junkies
Frankly, we don't expect most players to miss the majority of these games all that much. However, there are a few decent -- or at least big-budget -- titles on that list, such as Syndicate and Star Trek Bridge Crew. If you were hoping to play them on PS5 to get smoother framerates or other minor enhancements, it seems you're out of luck.
Finally, we've got cross-play, and it's another short list, only consisting of Rainbow Six Siege and For Honor. Both of these games will be getting next-gen upgrades, and they're the only two multiplayer games in Ubisoft's catalog that will let people game together across console generations.