Cadillac's plans for a new, range-topping, rear-drive flagship sedan are no secret; the questions lie in the details. What will it be named? When will it arrive? And what will it look like? The last question, at least, we can give a partial answer to: it will look like this.

Or, at the least, it will bear these proportions. The camouflage cladding the exterior of the Cadillac flagship sedan obscures much of the details, but the outlines are there, and for the most part, they reflect an up-sized take on the new CTS's proportions.

Looking more closely at the details, we can see multi-part LED lighting at both the front and the rear, a multi-bar grille under the netting masking the nose, a rather long wheelbase with an apparently large rear seating area, and, while it may not yet be final, dual exhaust outlets offset to the passenger side.

As for the larger outlines, the upcoming Cadillac flagship wears a long hood, a raked windshield, and rear glass that slopes gently into a very short deck. In some ways, the proportions recall the Elmiraj coupe concept--and that's how the spy photographers, who have seen it in person, refer to the car. Underpinning the car is likely to be a new Omega platform for large cars. This platform is thought to share much in common with the smaller Alpha design, including a rear-wheel-drive layout with optional all-wheel drive.

As for what the Cadillac flagship's actual name will be, it will likely adopt some three-letter descriptor that reflects the rest of the Cadillac sedan and coupe lineup. Among the possibilities is the LTS moniker, which GM has trademarked for Cadillac's use.

2016 Cadillac LTS flagship sedan spy shots

2016 Cadillac LTS flagship sedan spy shots

As the Cadillac LTS, or whatever the flagship will be called, will have to compete with the top tier of the world's luxury sedans, including the Mercedes-Benz S-Class, BMW 7-Series, and Audi A8, it will need a powertrain built to match. The twin-turbocharged V-6 engine found in the Cadillac CTS Vsport is a very likely candidate, as is the standard Cadillac 3.6-liter V-6 engine as a base configuration.

A top-tier model may use a variant of one or both of the latest-generation 5.3-liter or 6.2-liter V-8s from GM, which feature Active Fuel Management (cylinder deactivation) and direct injection, among other improvements to enhance gas mileage and power. A hybrid drive system is also highly likely, though what form that might take--whether Cadillac may draw on its experience with the ELR or move in new directions--remains to be seen.

While the Cadillac flagship has long been billed as a rear-drive sedan, it will also likely be available with all-wheel drive. An eight-speed automatic transmission is also likely to be standard across the line. There is also the possibility that Cadillac will expand the LTS range to include a full-sized coupe, much like the upcoming Mercedes-Benz S-Class Coupe. Best estimates for the Cadillac LTS' arrival are around the 2016 model year.

As always, we'll keep you updated with the latest information on Cadillac's flagship sedan as more information develops, and as our spies bring us new photographs.

_______________________________________

Follow Motor Authority on Facebook, Twitter, and Google+.