It depends on the type of business entity they have, but it is likely that it is in some form where the profits and (in this case) losses would "flow through" to your individual return. Thus I would hold off on filing taxes yet, but not because they are still deciding what to do this year, but because last year's expenses should be appearing on your personal returns. I would suggest getting that sorted out before worrying about what they do this year, which will be important for your 2021 taxes, filed in 2022.
Hopefully your husband has documentation to show that this was a real attempt to start a business, and not a hobby, you can't deduct hobby losses. You don't need to provide that with the tax return, but should have it if audited.