Actually prosecuting a sitting president was always nearly impossible. The immunity thing has to do with what happens after the president is no longer in office, doesn't it? Also, he only has absolute immunity for official acts. So then the question is what constitutes an official act.
And realistically the Supreme Court will eventually reverse itself, assuming that the democracy somewhat survives another decade, which is a good question. Because their ruling about absolute immunity just made no sense. But even if you think it did make sense, there are so many cases that have to go to court to be resolved. If the courts rule against a specific action and the president reads the court order and then does the bad action anyway, does it count as official? I think we can argue that it doesn't, because the courts specifically clarified that it's not allowed. But the president's attorneys would argue the opposite. So then it has to go back to the Supreme Court.
Assuming Trump stays in good health long enough to leave the White House, I think it's unavoidable that the above situation will occur.