These rumors are not true about him leaving Juventus because his performance at Juventus was not bad at all.
Allegri could make his team race for the title with Napoli but the bad atmosphere in the team after the penalty had a bad effect this made Juventus to had a bad performance in some games which is not coming to blame Allegri for it.
You will not see that happens again soon. Juventus has been solved all of problems with FGIC and UEFA. Juventus may not able to perform in european competition this year but juventus will be comeback strongest after next year. It's caused by juventus sees potential for another sanction to come. Allegri deserves to be treated even better. So many judgement was coming for him. He has become victim from old director's fault by doing some shady things to manipulate the financial of club.
Juventus will be reforming its club again for upcoming season. Some players gonna be sold to the another club and juventus is preparing for regeneration to come again very soon. I can't wait that to happen.