The 2014 Lexus IS sedan is scheduled to debut at the Detroit auto show this January. The first wholesale redesign of the model since 2006, the new IS has been redesigned from nose to tail. On our prototype drive, Lexus revealed a lot about the IS, but the styling is one of the many secrets the brand was not ready to reveal. From what we inferred looking at the camouflage-covered cars, they appear to borrow heavily from the current IS and the latest GS.

The borrowing continues under the new skin. Lexus did disclose that the ’14 IS will be built on a smaller version of the GS platform. A shrunken GS equals a larger baby brother, but how much larger? Good question. Lexus wasn’t ready to give up exact dimensions, but the interior feels more spacious than before, especially the rear seat. We’d wager that a longer wheelbase is a certainty and we’d guess that has been stretched a couple of inches from the current 107.5-inch wheelbase.

Lexus did reveal that the rear suspension has been completely redesigned. Like the GS, this IS has a compact rear suspension that separates the shock and spring to increase trunk space. In front, the control-arm suspension appears to carry over with the exception of reworked mounts for the anti-roll bar. Electrically assisted power steering returns, but Lexus has tweaked and strengthened the rack components to improve steering feel.

What we noticed first on our brief drive of IS prototypes is the seating position and the deeply bolstered seats. Lexus moved the hip point downward compared to the outgoing car. You sit lower than before and the steering wheel is more vertical, like a sports car. The interior design copies the shape and materials found in the GS. Push the start button and the instrument cluster lights up. A central-mounted tachometer, similar to the one in the LFA supercar, swings into position and illuminates its LED screen. Turn the Sport **** between the seats to select Sport mode and the tachometer changes from a black-on-white face to a white-on-black face.

Engines carry over from the current IS. The IS350’s 3.5-liter V-6 should have 306 hp and the IS250’s 2.5-liter V-6 should put out 204. An eight-speed automatic is standard with both engines—the slow-selling manual IS250 is dead. All-wheel drive will be available with both engines. A hybrid version, with a 2.5-liter four-cylinder and electric motor, will be sold outside North America. With the hybrid CT200h and the ES300h already on sale, Lexus doesn’t see a need for the similarly priced IS hybrid in the States.

We drove F Sport versions of the IS350 and IS250. Like the GS350 F Sport, the F Sport IS receives a unique front end, larger wheels than stock, summer tires, and firmer shocks and springs. IS350 F Sport models will offer active steering and electronically adjustable shocks. All IS models are available with Drive Mode Select that allows the driver to tailor powertrain responsiveness to thriftiness (Eco), regular operation (Normal), or friskiness (Sport S) by twisting a **** behind the shifter. When equipped with active steering and shocks, an additional Sport S + mode also changes the steering (quicker ratio and heavier effort) and shock (firmer) settings.

Driven back-to-back with the current IS, the new car proves to be the more stable of the two. It’s likely that overall grip has increased, but some of the IS’s playfulness and character has been excised out of the prototypes we drove. It’s a small difference, and one that likely can be chalked up to the heavier GS-based architecture—which is up to 176 pounds heavier. We’ll withhold final judgments until we drive the production-ready IS lineup, though.

On sale next summer, the IS250 and 350 will be joined—probably in mid- to late 2014—by a new IS F. A new-gen convertible is not yet confirmed, but remains a strong possibility. A coupe version, hopefully previewed by the stunning Lexus LF-CC concept shown at the Paris show, is reportedly still being studied.