it's most likely that vinicius will still retain his current position since it's obvious he does better as a winger than any other position. It's ok likely going to be that Jude Bellingham would shift a bit towards the midfield and will play a more free role assisting the the defense and the attack and for me, that's what works well for him. He can be doing all the dirt jobs and become an invisible attacker that still find his way to the front of the goal post unexpected. That's almost what he did yesterday in the England game and while Harry Kane stood as the top man for the goal scoring job, he came from behind to score the wining goal for England. Vinicius, mbape and Rodrygo will stand as a three man attack with mbape playing from the top 9 position while Rodrygo and vini would have to maintain there old positions.
Anceloti is a good coach that knows how to manage players well and this won't be a big deal for him to work with.
I have no doubt that Ancelotti as a coach has quite a lot of brilliant ideas in arranging formations. Mbappe's presence will provide additional good ammunition, creating many alternatives for coaches in choosing a spearhead. I think Rodrygo will be left out of the starting 11, possibly Mbappe and Vinicius will remain as wing strikers and Bellingham will be used as a shadow striker or as he has played so far.
The joining of Mbappe makes El Real's attack line even more fierce and it seems difficult to stop their progress in the title race next season.