Rumors had been circulating that the 2016 Cadillac ELR would bow in Los Angeles recently, featuring, in Cadillac's own words, "engineering enhancements." The rumors and that quote are as far as it got – the updated ELR pulled a no-show in LA, and no one outside of the brand appears to know when it will appear.
GM Inside News says its sources at Cadillac pinned the ELR's absence on some autonomous driving features not being ready to reveal. According to GMI, Cadillac insiders say the upgraded ELR will be a "highly autonomous vehicle," and the company needs more time to gets its systems polished. The site says "it's not unreasonable to assume that ELR will be [the] vehicle" that gets Cadillac's Super Cruise technology, but that seems a lot more involved than "engineering enhancements," and in September Cadillac said we'd see it sometime in the next two years.
It's possible the wait for the 2016 ELR and its secrets might only be a couple of months: the next-generation Chevrolet Volt, which shares a platform with the ELR and whose engineering updates we know quite a bit about, is scheduled to appear at the 2015 Detroit Auto Show in January.