All bets are off.
Unless you’re taking affirmative action and choosing to end the relationship with your current web developer early, there’s a very good chance that most (if not all) of your project’s timeline (and contingency) has been eaten up already. That mean’s that tomorrow’s big launch is not going to happen. Even if your deadline is a week away, you need to relook at that deadline and see what more time you can add to give your new WordPress development team time to not only action any remaining changes but also to get up to speed with how your site (as it stands) has been put together.
Its a bitter pill; I get it. But if you don’t swallow it now, your next WordPress developers might feel under such pressure to deliver that they’ll cut corners – something that is likely to hurt you in the long term.