And it Turns out the are for sure on the State level. And I don't think there is a limitations Statute at the Federal Level either for Tax fraud. But charges will be civil not criminal. Zero chance he'll go to jail for this. Had they caught him earlier of course, he could easily have done jail time for such flagrant and intentional violations of the tax code. (There are statutes of limitations on criminal charges.)
First, they have to prove it. Second, it has to make its way through court (you know Trump will throw everything he has at it). If, and we're talking a big IF, it gets to the point where Trump is determined to owe something, it'll be settled.
If the intent is to get a few bucks from Trump, it has a coin flip of working. If it is merely to toss dirt at Trump (let's face it, that's why the NY Times exists these days), those against Trump won't change their opinions, those with him won't either. It'll be a zero effect. Folks like myself, who think Trump is a buffoon but like much of what he's doing will still probably vote for him in 2020 - unless the Democrats can nominate someone sane, credible and moderate.