Yeaps, i saw 6878X as well too. 
But yeah, I was thinking a 3-way swap between the SP+Sv 38+Sv 229
fleet (if you get what I mean since 6878X is SP), but I've yet to
find any Sv 38 bus that's consistently MIA yet (that would hint
it's out to SP). Which was why I think should KIV awhile more
8669U more or less confirmed out to SP based on spotting by
other members and myself.
6878X should be the replacement although I can't be certain yet
as I did not bus spot too much lately, pls share if u have any info
(: