Perhaps when they introduced the LP Junior Tribute, thinking it might fill the niche? But I cannot really remember discussing a production stop here (maybe they paused production for a while to concentrate on manufacturing the Tribute to see how it goes). It would have been an incongruous move (not that Gibson hasn’t been good for those in the past!). TBird and SG are in the Gibson galaxy what P and J are in the Fender universe. I don't see them ever reintroducing an old, much less designing a new bass body shape that might supersede these two classics in sales. And they certainly do look radically different enough from a P, J or a Ric, no mistaking them. They are also nicely complementary, if the TBird is too huge for you, the SG is a suitably compact alternative.
Is there a more commercially established short scale bass on the market today than the SG Bass other than perhaps the Höfner which is however lumbered with the baggage that anyone who owns one will always have to explain why (s)he is not playing Beatles music [if (s)he indeed doesn't, but I have yet to meet a bassist brethren who owns a Höffie, yet thinks the Fab Four and especially Sir Paul are crap!]?