It would be too hasty if Juventus showed someone other than Motta, considering that so far he has shown Juventus' status is quite good and is still strong in keeping the distance from Lazio 2 points. The title hunt is still quite early and we might still see a change of position especially to secure a ticket to UCL next season. So let Motta finish 1 full season rather than planning to be replaced by Xavi. I know Xavi is a competent replacement figure but Motta is also still worthy as Juventus coach.
I don't think Juventus would bring in another coach and sack Motta at this point my reason is that they're getting close to the end of the season and motta is in a good position, even though it's threatened by Lazio, they'll give him till the end if the season to see how far he'll go if he'll close the gap and win the scudetto or qualify for the Champions league in a good position, like runners up or third, those are the things that could determine if they'll employ a new coach or not.
If Thiago motta fail to accomplish any of that any finish below the position meant for Champions league Qualification, then Juventus board would have no option than to sack him. Xavi Alonso is a good coach anyways, he was successful in the Spanish League and won a trophy for Barcelona even though he got sacked due to some circumstances, I feel he'll make a good choice as coach during the summer if Motta doesn't meet the boards requirements.