I linked my batlle.net account to transfer to steam before I set up cross-save. My xbox has my main characters so when I set up cross-save I selected those characters and now I can play on battle.net with those characters. When I look at my account for my transfer to steam info, it still has my old battle.net characters shown for what is transferring to steam but shows steam listed under my cross-save accounts. When destiny switches to steam will my xbox characters show up on steam because of cross-save or will my old battle.net characters show up since that is what shows for my transfer info?
The Migration is a separate thing from Cross-Save. The Migration is just Blizzard to Steam; the account you currently have set as your main cross-save account has no bearing on the migration. When Destiny 2 migrates from Blizzard to steam, all of your Blizzard Destiny 2 data (licenses and save data) goes with it. After that, your cross-save will kick in and when you play on Steam, you'll be using whatever characters you have set up for cross-save, which in your case will be your Xbox characters.