Depends on what's in there. It's a Pandora's box. There is most definitely tax fraud going on and it's going to be massive. There will most definitely be a paper trail for money laundering which will most likely be for russian players. There will also be embarrassment from his failure as a "business" man, and his fractional net worth, are shown to everyone, but his obvious cult members won't care.
The SCOTUS hearing isn't about public release of his taxes, which is what my last sentence is hitting at. The hearing is about state prosecutors getting the taxes, not about public release. Though, I would HOPE someone leaks them. Once they leak, reporters will go nuclear and uncover a trail like never seen before. I really hope they are leaked, but that's an argument trump's lawyers are trying to make against prosecutors getting them.