It is very likely that Enrique will try to find replacement for Mbappe, but there is no certainty who will really be worthy to replace Mbappe in the PSG squad considering that they are team that has great players who really retain them.
If Enrique doesn't immediately look for player who can replace Mbappe, I also doubt that PSG will be able to play well, especially in an important competition like the UCL.
Everything running low and this is really out of the picture. We've come to realized that Kylian Mbappe was the most valuable player in Paris Saint Germain and also in the general Ligue One. He's unstoppable and on fire each time he's with the ball. PSG headcoach, Luis Enrique will not depend on Kylian Mbappe because there's quite more to deal with and winning become straight and easy going. Who's Kylian Mbappe replacement? Perhaps none for now and his absence will really affects the club's performance and stats next season.
I think this will also have an impact on broadcasting rights where Ligue One will decrease in popularity after Mbappe's absence from next season. On the other hand, most people will also start to talk less about Ligue One if Mbappe is not there and that will clearly be a loss for them.
However, Mbappe wants to upgrade his career at a better club and he wants to chase the title he has never won during his career. Luis Enrique will also certainly be confused but I'm sure he will soon find the right replacement solution for Mbappe. If we look at the list of players at PSG, I think there is no player who can replace Mbappe's role so they will transfer new players this summer. That's the only option currently available to PSG and they are certainly well aware of that.