if you look at the Grimaldis history, you will see that they wouldn't be called Grimaldi anymore, but instead Polignac-Matignon, which is their heritage. Rainiers father was a Polignac who married Princess charlotte who had been illigitimate but later been recognized. If my info is correct, her husband was adopted by Louis so he could legally take the name Grimaldi, similar to what the Wasas in Sweden did with Marshall Bernadotte.
So he would probably take his mothers maiden name. But Albert isn't dead yet and might still produce an heir or heiress.
