This is a good new to Moto X users who are on Sprint. You will be elated to know that Android 5.1 update is coming to your Moto X on Sprint.
The new Android 5.1 update for Moto X on Sprint has the software version LPA23.12-39.10, and you should start seeing the update by now.
Without any doubt or prejudice, Android 5.1 update will bring to your Moto X new Material Design, quick settings changes, device protection, and a Stagefright exploit fix.
This update was released few days ago and you should have seen the update now.
And if your case is that: you have not seen the update and your Moto X is on Sprint, then you can do a manual check for the update.
Have seen Android 5.1 update on your Moto X on Sprint?