Sequel game systems?

[Voadam]

Some have theorized that White Wolf's Exalted was intended to be a mythic prehistory for the World of Darkness the way Earthdawn was super distantly connected to Shadowrun. I don't really see any setting or NPC connective tissue between the two besides the d10 rule system, but I am not a comprehensive master of deep cut lore on both that might show such a connection.

 

[Voadam]

In addition to potentially going from Dark Ages Vampire to Victorian Ages Vampire to modern Vampire the Masquerade with potentially the same character, you could go Ars Magica to Dark Ages Vampire with their shared setting and history, switching from one game rules system to the other if the party of mages get turned into vampires.

 

[Alzrius]

There's a notation in AD&D 2E's Arcane Age: Netheril: Empire of Magic (affiliate link) which says that you should use its alternate rules for the Forgotten Realms campaign setting prior to the Fall of Netheril, after which you should use AD&D 1E up until the Time of Troubles (which were a trilogy of novels as well as a trilogy of adventures), after which you should use standard AD&D 2E.

This should be just one of several instances of settings having in-game instances of major upheavals being the justification for new editions:

• WG8 Fate of Istus was Greyhawk's justification for moving from AD&D 1E to 2E.
• Die Vecna Die! would be an AD&D 2E to D&D 3E update for the main D&D multiverse, whereas The Apocalypse Stone was meant to be the changeover for homebrew campaign worlds.
• The Spellplague updated the Forgotten Realms to D&D 4E; it had several novels, but no modules set specifically during the changeover. The same formula would follow for The Sundering, which brought FR into D&D 5E.
• Dragonlance would be converted from AD&D 2E to the SAGA System during the events of the Summer of Chaos; this was mostly covered in the novel Dragons of Summer Flame, though there'd be a few adventures (e.g. Seeds of Chaos and Chaos Spawn) set during the same events, albeit not with central roles in what was happening.
• The War of Souls trilogy of novels would bring Dragonlance back to D&D 3E.

 

[Alzrius]

An interesting notation is that Pathfinder 2nd Edition could be considered a sequel to Pathfinder 1st Edition due to the campaign world (Golarion) being presented in PF2 as if all of the adventure paths written for PF1 had already happened.

A fun little side note is that, while there was no in-game upheaval event to mark the change from the PF1 to PF2 rules set (Doomsday Dawn is the closest there was, being a "playtest adventure" for the new edition), Legendary Games published their third-party adventure Sentence of the Sinlord (affiliate link) which presented an alternate ending for the Return of the Runelords adventure path (the second-to-last AP for PF1) where it creates an in-game justification for changing various aspects of the rules (proposing that it could function for introducing third-party magic systems which hadn't been used previously, or changing the game rules altogether to mark the beginning of using PF2).

 

[Thomas Shey]

You could make an argument for this for various editions of Shadowrun.

 

[Staffan]

Some have theorized that White Wolf's Exalted was intended to be a mythic prehistory for the World of Darkness the way Earthdawn was super distantly connected to Shadowrun. I don't really see any setting or NPC connective tissue between the two besides the d10 rule system, but I am not a comprehensive master of deep cut lore on both that might show such a connection.

The big hint is the back copy on the original Exalted book, which starts "Before there was a World of Darkness, there was an age of savage adventure."

But that said, you have to squint pretty hard to see the connections. The strongest thematic connections are probably the shape-shifting Lunars and the potentially vampiric Abyssals, but you also have some in the reality-warping Sidereals who are supposedly the connection to Mage. But the connections are more thematic echoes than being a direct prequel – I understand the original plan was to make the connections more explicit, but at some point they decided the game was better off standing on its own.

However, there were multiple games released that were direct prequels of the modern World of Darkness games. Vampire: The Dark Ages is probably the best known, but you also had Mage: The Sorcerers' Crusade and I think there was also a Wild West version of Werewolf. In addition, Vampire/World of Darkness itself was a potential sequel to Ars Magica: one of the vampire clans is named after one of the Houses of Hermes in Ars Magica (Tremere) and they deal in weird blood magic that most other vampires don't have any truck with, and the Order of Hermes is one of the Traditions in Mage, and I think some of the background lore refers back to Ars Magica.