It is unreasonable for the software vendor to impose the task of converting a large mass of files (one by one!) on the users, especially within such a limited time frame. Most users have hundreds, thousands, or more such files to go through. As things stand, a very large amount of music is certain to become lost. A freeware convertor would obviate this particular concern. Very easy to implement, too; just don't disable the export and print functionality anymore in the main application after the "evaluation period" expires.
Are you sure Finale has no batch export? There are free & paid tools available on both Mac & Windows to help automate menu actions and batch convert things.
The product is dead, and like any product or business that dies, yes users may have a problem with their archive. It does suck, and I feel for anyone in this situation. I guess the lesson is that this is always the risk with all software, it might lose support. It happens, often.
I don’t see any reasonable alternatives. It doesn’t seem reasonable to demand that someone ending support for a product must turn around and write a new product to continue supporting the dead product. If they’re out of money, they’re out of money, and they can’t afford to retain developers to work on it.