Cadillac will call its new flagship sedan the CT6

Cadillac is calling its new hi-tech flagship sedan the CT6.

This is the fullsize sedan that will be built at General Motors' Detroit-Hamtramck assembly plant starting in late 2015. The rear-drive car will be bigger than the XTS and will compete with the BMW 7-Series and Mercedes-Benz S-Class.

The name, which may be confused initially with the midsize CTS, signals a "coming shift to a simplified naming convention for future Cadillac models," GM said in a release. "CT" will designate car models in the future and the number 6 gives the relative size and hierarchy of the car. Under such a model, the XTS might become the CT5 in the future and an even larger model coming later this decade could become the CT7.