The 2013 Cadillac XTS will share its basic platform with the 2010 Buick LaCrosse, shown here. See more pictures of the 2010 Buick LaCrosse.

We knew it was coming. Now the replacement for Cadillac's slow-selling DTS and STS premium sedans is finally coming into focus. XTS promises to be better than both, but can a bigger, plusher Buick LaCrosse lift General Motors' flagship-brand sales?

What We Know About the 2013 Cadillac XTS

We've known for some time that General Motors planned to replace Cadillac's slow-selling DTS and STS with a single premium large sedan, but could only guess what the new model might be like. Now, thanks to an online report by Canada's National Post newspaper, we have a much clearer picture of what should emerge as the 2013 Cadillac XTS.

General Motors made a surprisingly speedy trip through bankruptcy court, a process that involved selling the most valuable assets of the "Old GM" to a "New GM" owned by the U.S. and Canadian governments, an auto-workers health-care trust, and a bondholders group. In exchange for government aid, GM agreed to guarantee employment at certain plants, including its Canadian complex in Oshawa, Ontario. The 2013 Cadillac XTS is one of four new vehicles that GM promised to build there. The others are a 2011 Buick Regal midsize sedan, a North American version of the recently launched China-market model; a redesigned Chevrolet Impala midsize sedan, slated to start production in early 2013; and a hybrid vehicle of some kind, perhaps based on one of the above. Oshawa is also the sole source for the 2010 Chevrolet Camaro and is racing to keep up with early-days demand for that reborn "ponycar."

Significantly, the four new Oshawa models share the global Epsilon 2 midsize car architecture that was developed pre-Chapter 11 as a joint effort among GM's European, Asian, and North American operations. According to the National Post, the 2013 Cadillac XTS will be a "stretch" Epsilon, suggesting a larger and plusher sedan than the Epsilon-based 2010 Buick LaCrosse (badged Allure for Canada). That car is built at GM's Fairfax plant in Kansas City, Kansas, alongside the Chevrolet Malibu. The reason XTS, Regal, and the next Impala are coming from Up North--other than GM's need for financial support from Ottawa--is that Oshawa has greater flexibility for building vehicles of different types and sizes. That's especially important now. As an unnamed GM source told the National Post, the company must be able to "juggle the production mix to meet the market" if it hopes to be profitable again and pay back its loans. "That is something that GM has not had the full-scale opportunity to do," the insider noted. "In the past they've built assembly plants dedicated to one vehicle, they run the piss out of it, and they throw money to make the public buy it...That's passé. That's the bad old days we hope will never come again."

Flexibility is a hallmark of the E2 architecture itself, which comes in three basic sizes. The 2013 Cadillac XTS is designed on the largest variation, no surprise for the new flagship car at GM's flagship brand. The Regal uses the smallest version, the LaCrosse and next-gen Impala the in-between size. We've extrapolated XTS dimensions from those of the LaCrosse as well as the redesigned 2010 Saab 9-5, another "big E2" model.

Regardless of size, Epsilon is engineered to accommodate front-wheel-drive and all-wheel-drive powertrains, so we expect the 2013 Cadillac XTS to offer those choices. That compares with the outgoing STS, built on GM's Sigma platform with rear-drive and AWD, and the front-drive-only DTS, whose structural roots date from the late 1990s.

As far as we know, however, the E2 platform cannot accommodate a V8 engine, so look for the 2013 Cadillac XTS to come with the top-line LaCrosse option, a 3.6-liter V6 with economy-boosting direct fuel injection. We suspect this new corporate mainstay will be tuned up some for XTS duty, adding at least 20 horsepower and 16 lb-ft of torque over Buick's version, partly to compensate for the Caddy's expected greater weight. Only one transmission is likely too, the same 6-speed automatic used in most every other U.S.-market Epsilon-based model.

For more inside information on hundreds of new cars of today and tomorrow, check out:

• 2010 Buick LaCrosse Review and Photos
• 2009 Consumer Guide Best Buy and Recommended Award Winners: Check out which cars won our Best Buy and Recommended awards for 2009.
• Future Cars: Step into the automotive showroom of tomorrow with reviews, analysis, pictures, and preliminary specifications on scores of vehicles that will be appearing next year and beyond.