Ever notice that whenever it is said that a 'famous person' could spend up to 'X' years in prison, it never happens?
It doesn't come close to happening, either. They are immune, sadly.

As for ol' Boris... I'm pretty sure that he's done several things in his life that are worse than tax evasion.
He's not the sharpest knife in the drawer.... But even at that, a lot of his troubles stem from his pure arrogance that nothing bad can possibly happen to him. While that may be true from a legal perspective (sadly), when you have millions of dollars and then proceed to lose it, there aren't too many lawyers who can get it back for you.