As you may have seen already, we have updated the X-Cart 4.x roadmap recently:
http://help.x-cart.com/index.php?title=Roadmap
We've decided to completely remove Advanced Statistics module because it became outdated and can be substituted by services like Google Analytics, freeing a lot of space in your database and improving the store performance.
The Bestsellers module will be redesigned to use it's own data, so it will not require Advanced statistcs enabled anymore.
It is recommended to start using Google Analytics or any other statistics service right now because after upgrade to 4.6.2 old module data will be erased from database.
See the Google Analytics manual for details:
http://help.x-cart.com/index.php?title=X-Cart:Google_Analytics
Anyone who still want to use Advanced Statistics may edit upgrade packs removing the deletion of module. We'll provide per such request a list of files/queries that should be kept.