Yes, Nadal will definitely the favourite in Paris, but here comes the next generation of young and very aggressive tennis players just pulling Nadal's coat now and will go for him in French Open.
Zverev will likely be the second odds favourite, Thiem, Tsitsipas and then Berrettini. We don't know how long can Nadal hold, because in the last 2 clay tournaments he was upset as early as QF if I'm not mistaken.