IMO my expectation is that they not do that. If they want to offer hot-swappable batteries, they should either do it right (with a more functional battery management IC or a little homebrewed FET-switching circuit), or they should at least come up with a hack that doesn't threaten the battery safety. For example, have a physical switch to select between the two batteries and instruct the user to flip it when one gets low. Use a super capacitor to cover the short time while the switch is between connections.