From the What is Java Auto Update? How do I change notify settings? article:
Why is the Update tab missing from the Java Control Panel?
Java Auto Update is currently not available for 64-bit versions of Java. 64-bit versions of Java do not include the Update tab in the Java Control Panel.
Guess you'll have to do it manually. Given the sheer number of security issues with Java of late, not having auto-update support x64 is a real head-scratcher.