I don't think upgrading on Bentancur would bring us much further. This season he has been one of our best players in many games despite only being 21. He currently plays as a top class box-to-box and he puts so much energy and drive into our midfield. Yes we might find a player who currently could contribute a bit more, but at the end of this season with the growth rate of Bentancur, who knows.
However we currently have a VIP 'regista', who doesn't dribble nor defend, mostly opts for easy backpasses and occasionally delivers some great vertical passes. I don't think we can afford playing with Pjanic. It made sense for Pirlo, as he was a genius who absolutely killed it in that role, delivering cutting through balls and vertical passes with his eyes closed. He beat his marker with ease, to launch an attack and drive us forward, as a player like Pogba also does. Pjanic currently has the most touches per game and is in his role the most important player in midfield, if not in the whole team. I think he is a limiting factor in our midfield and must be replaced first, if we want a leap in quality. Things are going to be the same with him, even if we get Kante instead of Bentancur.