I don't expect Tuchel to be sacked because he has only been in Munich for a few games, as you said he came at the wrong time, so there is defeat and chaos of course tuchel will be the most to blame, I think tuchel hasn't found a good formation as he should he hopes so just wait to see Munich in the next few matches and hopefully he can bring Munich to win the German league this season.
And now Bayern only playing at bundesliga only and their position also doesn't really good especially after defeated by Mainz their position were taking over by Dortmund and imagined if Bayern has failed to showed their consistency and Dortmund being an the champion of bundesliga and i am sure Tuchel will be sacked this summer
You will see that when the time comes, specially after this season is over and during the off season training period, he will shape this team how he wants them to be. This season all they have to do is win the title, that is still very much on the table and could happen, just win all the other games and you will be able to get the title I am sure Dortmund will end up losing points eventually.