If Messi comes back to Barcelona next season I'm pretty sure that he would do his best for the team. I don't think that Xavi would change his strategies to build a game based on him. But he would surely find the right place for him in the starting eleven.
Messi will quickly find his game with Barcelona, moreover the current coach is his teammate when gaining success when they played together first. There is not much difference from Xavi's current strategy, it can be said that he adopted the gameplay when he played before and he applies it at Barcelona now. Of course, Messi has memorized the strategy used by Xavi. In addition, Xavi will also definitely give freedom to Messi, in other words he already knows very well his ability to cultivate the round skin.