Any narrative justification for the physics of the entire universe suddenly changing is going to be ridiculous.
Well, the original physics of game universes are pretty rediculous to start with, so I don't see a problem with that

Presumably virtually every group trying a new edition starts a new campaign anyway.
I haven't followed metaplot, but I've played with several groups through edition changes. We didn't start new campaigns for the purpose. Not 1e to 2e D&D. Not in changing editions of Shadowrun, not in changing editions of White Wolf games.
What's wrong with good old-fashioned alternate realities? 1e Forgotten Realms, 2e, 3e, 4e, 5e... just let them all be 'shards' of the same reality. Don't try to shoe-horn changes between editions into the same timeline.
The thing is, there are folks out there that are kind of invested in the timeline - either for their own game, or in being a fan of fictional tie-ins. These folks don't want to see the original timeline vanish.
But I don't really care about Drizzt and book continuity seems like a dumb reason to bend the metaplot around a new edition.
Dude! Book continuity is *money*. Every single one of the Salvatore's 18 Drizz't books has made the New York Times best seller list! Is cold, filthy lucre not a good reason to bend things?