Don't just launch the changes. Make an event out of them. Tie the changes into story.
For example, a while back, Franklyn Richards dramatically changed superheroes and their lives in the comic world, even moe dramatically than you're doing in game. There will be bugs, as their always are, but these would be glitches in Franklyn's pocket universe. IF all goes well with the changes (and you don't lose business) the change sticks. But if for any reason this turns out to be the New Coke disaster of years gone by, you have an easy out to return the world to "normal." Just a thought ...