For XC racing?... Common yes, but not the standard. The standard is still 80 mm. Just like hardtail frames are still the standard albiet full suspension is common on race day.

I just wanted to differentiate between choices of 4" and 3", hardtail and full suspension. If Mooch wants a dedicated race bike then he'll probably go 3" and hartail. If he wants a play bike to race on then the conventional wisdom (in my neck of the woods) says 4" and full suspension.