They likely have been married merely for the public image of both parties for the last X years, and have finally arrived to the conclusion they don't need the facade any more. If I'm right with this assumption, and if all the "conspiracy theories" about Gates are correct, then this could be a somewhat worrying sign as he is close to achieving whatever he wants and doesn't feel the need for any kind of pretense in the public.

(No one is married to a man like Gates as long as his wife has and not know what he is involved with, so you can forget all theories about his wife suddenly finding out "the truth". They're both guilty as hell...)