So I am curious. I have been DMing for decades and I don't know if I have ever used "multiverse" storytelling. While PCs have done some planar travel, especially when I have run Ravenloft or Planescape stories, I don't think I have ever had PCs traveling from one setting to another, as in, I have never had players transported from Krynn to Toril for example. But with the emphasis placed on the concept with recent releases, I am curious. Am I an anomaly?
So have you done worldhopping as a feature in a campaign? Care to talk about it?
It's funny to hear everyone screaming "never!!" when in my experience most DMs easily send the PCs to other worlds which
technically aren't considered different settings only because they have a "inner plane", "outer plane" or "demiplane" label slapped on them... but in many cases end up seeing the same
kind of adventures being played.
There might not be much motivation to travel from actual Toril to Oerth to Krynn with the same PCs. One reason could be because the similarities are so vast that adventures would hardly feel different. The other reason is that each setting has a strong appeal when played long and intensely by the PCs: for example playing your way up into Faerun organizations, or navigating the conflicts of Planescape factions. This is lost if you just hop into it for a single quest and then leave. Better to have a whole campaign in one base world, and next campaign in another to appreciate them both. In our current campaign I've used published adventures, some from Forgotten Realms and some from Greyhawk (and some settings-less), but there wasn't much motivation to plane shift between worlds, so we just jumbled stuff together and pretended we're always on Faerun (just because its overarching themes and features had already been established).
A trip to a significantly different world is potentially more interesting, but there has to be a striking selling point: it could be the absence of gravity of the plane of Air, or the automatic resurrection of Ysgard, or the unique take on magic of Athas, or the trappings of Ravenloft. It doesn't matter then whether those four planes are "material", "inner" or whatever, they're all just different worlds.
Still I see no reason why I wouldn't want many "full settings" fantasy worlds to co-exist in my multiverse. In fact recently I have started a thread to gather my own thoughts on which worlds feel cool to have around. And if the PCs find a reason to want to visit the next planar neighbourhood, I'm not going to stop them!