My suspicion is the CT8 is delayed while other products are prioritized. GM didn't invest hundreds of millions into Omega for the CT6. I suspect the 7-passenger Omega-based crossover will be prioritized over the CT8.
You should have stopped right there
You neglect to mention the changeover to the new Alpha based, third generation CTS that occurred in for the 2015MY. The second generation CTS sales had been shrinking since 2011. Now introduce an all new CTS that moves upmarket and commands higher prices in a shrinking luxury sedan market and you get a 37% decline. As you said, even the established players in the market - BMW was down 16%, the E-class was down 25%. It sucks, you cry yourself to sleep at night because of it

, but not a surprise when you look at the market.
You've substantiated my point, I think. The Escalade IS the flagship car for the brand. Why does Cadillac have to build a six-figure luxo-barge to be the flagship? People want SUV's and crossovers. They already have the large luxury SUV that defines the category. MB built an image around the S-class. IMO Cadillac should build its image around the Escalade.
I don't work in the auto industry but it would surprise me if Cadillac had unlimited resources to develop every product they want at once. Priorities have to be set. Right now a large luxury sedan in a shrinking market is not a priority. Back to my comment above, why are you so insistent that the flagship product has to be a sedan? Because the Germans did 40 years ago?
Right, so buyers step into the showroom to see the Escalade but can't stomach it's $90k price tag...but right over here is the best selling 5-passenger luxury crossover that costs half as much..