I will bet that the new Cadillac flagship will debut in 2015 possibly as a 2016 and it will be the all new rear wheel drive S class / 7 Series fighter that will still be called XTS !! There is NO way Cadillac will have ATS- CTS- XTS - ?TS. The matchup is set. And remember the original SRX ? They totally redid the car on a completely different platform but still called it SRX.
So, IMHO XTS will be the new flagship and will be stunning