I know this has been implemented, but the functionality is really quite poor. It also needs a trigger pad and to put fades PRE SPLICE too because crossfades tend to cut off the transients. If you try to workaround by selecting everything and drag the fades back, it ruins the rest of the glitches it created, resulting in doing more manual editing. I just tried editing some drums in Studio One 5 and the autofill and crossfade feature is really bad. I have to continually delete portions of the event because it creates double crossfades, extra events, weird overlaps etc; I'm having to redo probably 60% or more of the hits.
Please have another look at this feature. I know it would make a lot of us who are trying to get away from Pro Tools much happier if Studio One could compete in the editing department. 
Pro Tools is just practical in it's editing. I say that as a guy who just wants to track, edit, and mix efficiently.
In the meantime, Studio One has come a long, long way since I even tried it back on version 3. I now own version 5 in hopes of this becoming just as good of a digital tape editing machine as Pro Tools. Thank you for what you've done thus far.