Rudi Garcia confirmed replace Spaletti position as Napoli head coach although he doesn't has good reputation after sacking by Saudi Pro League teams Al Nassr after failure winning domestic league tittle. But Rudi Garcia have experienced with Serie A because last several years he managed for AS Roma head coach and he not difficult for adapting with Serie A culture.
Massimo Allegri as Juventus position seems secure and not any rumor his position will replace by Spaletti, Juventus is typical teams won't to pay compensation for head coach and sacking Allegri before his contract over until 2027 will spent much money have to pay for Allegri's compensation. Seems not change with Juventus head coach and Allegri will safe his position for upcoming one season later.
Yes, Al Nassr sacked Rudi Garcia because he can't fulfill the target given by the team. It is not a good reputation, he failed to win the title in a smaller league. Now, he will manage Napoli which plays in of the biggest leagues in Europe. Although he is familiar enough with Serie A, it is not enough to lead Napoli to compete for the title. TBH, I doubt how Napoli performs in the next season.
It seems Allegri will stay for 1-2 seasons as Juventus manager. But it is not the best idea to keep him if he always failed to improve Juventus performance. I think the best way is to sack him very soon if Juventus has enough money to pay the compensation. Keeping him as a coach means keeping Juventus in bad performance.