I do think that Tuchel will play or try out the back 4 at some point but am not too sure if it is wise to constantly change formation in the Premier League, if his past is anything to go by. It may have worked in the Bundesliga and Ligue 1 for him but highly doubt it will work in England. I remember Guardiola used to tinker a lot with the formation when he first came to the Premier League but then he eventually stopped doing it because it was hard to get any consistency going.
To be fair to Tuchel, although we have stuck with the back 3, he has made small tactical tweaks along the way. We have played 3-4-2-1, 3-4-1-2, 3-4-3 and more recently 3-1-4-2. He has also made us play less of the nonsense slow, possession football and play a more direct style (not route one football).
Regarding Ancelotti, think the biggest issue with his second season was the squad. We let players go and did not buy new ones to refresh the squad. They were almost on their last legs, as proven in the 2011/12. That squad was also wedded to only thrive in 4-3-3, although I remember Ancelotti did switch to 4-4-2 in the second half of that season to get us out of the slump.
As for Conte, he did try to change to the 3-5-2 but think he was too rigid with the way how he wanted to implement it.