Why would they have custom migration code for something that is clearly in flux due to it being an unfinished beta feature? If they did something like that for every little API change they’ve made in the past couple of months it would be a full time job just writing migration. just find/replace in your keymap, this is the risk of using something that is beta.
Yes, blender upgrades can potentially break keymaps. As part of the update process, all of the official keymaps get maintained by the devs doing the breaking- any custom keymaps you have built are up to you.