Q. Bungie says that there will be no more host migrations, ever, in Destiny 2. Is that right?
A. Yes, it's true that that's what they've said. I'm not sure that I believe it, however. I certainly believe that what Bungie said will be true for PvP matches and for raids. For both of these cases, the console-hosted Physics Hosts of D1 did not always prove reliable-enough for a seamless experience.
On the other hand, the console-hosted Physics Hosts, in my experience, worked flawlessly in almost all other situations. Why fix something that's not broken? While at the same time spinning up expensive servers for no good reason?
Consider too the situation where you are playing the story campaign by yourself in an instanced Bubble. You don't need a remote Physics Host for this. Clearly, the entire game (except for the Mission Host) can run on your console. Why spin up a Physics Host in the cloud for solo play?
So let's assume for the moment, that when playing missions solo, there is no Physics Host,