Going to address this with point 3 because it's essentially the same thing. Bungie is private company. It is not a publically traded company like, say, AB is.
This means that Sony can't just barge in there and buy up their shares. Bungie can negotiate its own conditions for selling shares and one of those conditions is, considering Bungie's recent track record and the fact that Sony has publically and very specifically said that Bungie will operate as an independent developer/publisher, most likely that Bungie remains full control on how it operates and what/how/where it publishes its games. These conditions are legally binding.
That does not mean that Sony can't negotiate a deal with Bungie for exclusivity in the future. What it does mean is that Bungie will get the final say in it.
My initial response that started this discussion was to another poster that said he was surprised Sony didn't pull Destiny 2 from Xbox yet when, in actuality, they probably can't.
All a private company in Bungies case means is that shares are owned by employees rather than the public. Which is why Sony have an integrated retention plan where payments are deferred to employee shareholders
This means that these employee shareholders all voted to sell their shares, because Sony now owns 100% of the shares.
There is nobody but Sony within Bungie who has any voting power on decisions. Sony has left their management team in tact and allowed them decision making power on their own affairs, that is all that independence means.
There is no refunds in this scenario, there is no we changed our minds, there is no "you promised". Sony owns them, Sony does what they want.
But because they want Bungie to be a success, they will be hands off, and we know will treat it in that way because Sony builds good relationships with its developers, and they want Bungie to continue to operate in the way that's been successful for them
That said, the Bungie board also has a duty to act in the best interest of its shareholders. And it's shareholder is only Sony, who they are a subsidiary of, and Sony could easily sack the whole board and replace them if it wanted to be malicious