Thanks all. It def hasn't bridged and is still plenty alive. I was just curious if you can tell if roots are gonna shoot from the callous based on the looks of it.
Oh well, like all things bonsai, just have to be patient.
fwiw, I just checked on a Styrax air layer that ended up looking like that. I cut back almost but not quite all of the callus and re-buried it. I'll post some pictures when I get home