General Motors’ intentions in the light-truck market will become clearer Dec. 13 when the auto maker stages the worldwide debut of the all-new ’14 Chevrolet Silverado and GMC Sierra fullsize pickups in Detroit.

Speaking with journalists during the recent Los Angeles auto show preview, GM North America President Mark Reuss says the light-truck market in the U.S. will face a transformation as strict new corporate average fuel-economy standards ratchet up from 2016 to 2025.

Reuss says the regulatory environment, calling for reductions in carbon-dioxide tailpipe emissions, is forcing auto makers to explore all technologies and consider consolidating large and midsize trucks onto a single architecture.

But GM has a different strategy: Instead, the auto maker will produce the next-generation midsize Chevrolet Colorado and GMC Canyon pickups on one platform while the fullsize trucks will remain on another, the all-new K2XX architecture. Both employ body-on-frame construction.

First in the chute for the U.S. are the Silverado and Sierra, followed later in 2013 by the heavy-duty versions and then at the end of the year by the Colorado and Canyon, the auto maker tells WardsAuto.

Reuss tells journalists the light-truck market in the U.S. will undergo “a microsegmentation of the bandwidth” within the next five years, making it difficult for a single architecture to meet the needs of all pickup buyers.

“If you take one truck and try and create a bandwidth that spans everything, from powertrains to duty cycle, and try and do it at a cost-effective way and scale, it should be very tough to do.

You won’t be able to sell as many trucks because you will get penalized on a per-truck basis.”

Careful not to leak GM’s truck news before the Dec. 13 event, Reuss does say: “We will have a range of pickup trucks – our traditional Silverado and Sierra – and we will have midsize trucks in the market here. In that portfolio, we look at lots of different powertrain options maybe no one’s done before.”

He was hinting that a light-duty diesel engine is on the table for GM’s future pickups, without specifying application in fullsize or midsize trucks. “I think you’ve got to wait a bit,” he says.

Detroit’s three auto makers have been down this road many times over the past decade, considering and even developing modern, fuel-efficient diesels for light trucks – to slot below the heavy-duty diesels – but never bringing them to market.

GM this year launched in Thailand a re-engineered Colorado pickup powered by two new Duramax turbodiesels, a 150-hp 2.5L and 180-hp 2.8L, both derived from the 6.6L Duramax V-8 used in U.S. heavy-duty pickups. In Thailand, GM was expecting more than 70% of customers to pick the 2.5L diesel.

In the midsize pickup segment, Reuss tips his hat to Toyota for the long-running success in the U.S. of its Tacoma, which sold 127,335 units through November this year, outselling more than two-to-one the No.2 entry, the Nissan Frontier, according to WardsAuto data.

He says Toyota has succeeded by positioning the Tacoma as a “lifestyle” truck, as opposed to a fullsize truck more likely to be used for work.

“Toyota doesn’t sell that truck based on a big truck reputation,” Reuss says. “They sell it on the Toyota reputation, and they do a really good job accessorizing it and putting that into a place where young people can get it, affordability-wise.”

Interestingly, GM in Thailand is positioning the new Colorado pickup to meet recreational, lifestyle needs. Pickups are popular in the Thai market, where roughly half are sold for private use.

In the U.S., GM stopped production of the previous-generation Colorado and Canyon (designation GMT 700) in Shreveport, LA, earlier this year as the auto maker reduced manufacturing capacity.

GM has announced the new Colorado, which shares its underpinnings with the version sold in Thailand, will be produced at the Wentzville, MO, assembly plant, and in September the auto maker confirmed a new GMC Canyon as well.

A WardsAuto forecast schedules the Colorado and Canyon for 2014 as ’15 models and projects production reaching 75,800 Colorados and 21,000 Canyons in 2016.

Asked if the new Colorado/Canyon in the U.S. will be similarly sized to the trucks they replace, Reuss says they will be “quite different, probably be a little bigger. It definitely will be way different package-wise.”

But he suggests a unibody platform never was seriously considered for the next Colorado/Canyon. Honda entered the U.S. pickup market in 2005 with its unibody-based Ridgeline.

Honda tried to position the vehicle between compact and fullsize pickups, but the vehicle never gained popularity among core truck buyers who use them for work. Instead, the Ridgeline has appealed to lifestyle buyers who haul smaller loads, such as the occasional motorcycle or jetski.

“You’ve got to have trucks for people who make a living,” Reuss says. “What’s the lifestyle guys going to do when they want to tow and put in a motorcycle and tow a camper? You can’t do it. That’s been proven by one of our competitors.”