An electrified powertrain will help to ensure the GLS can compete in regions with strict emissions limits and survive into the era of new European Union CO2 limit enforcement, which will begin in 2020.
At the top of the range will be a Mercedes-AMG GLS 63 featuring a twin-turbocharged 4.0-litre petrol V8, likely with the same 612bhp output as it has in the S63.
Mercedes-Maybach GLS on the cards for 2020
Mercedes is also planning to expand its luxury Maybach line with a plush range-topping version of the GLS next year.
The Mercedes-Maybach GLS will be marked out by unique vertical grille slats, chrome exterior detailing, unique wheels and distinct badging. The biggest changes will be to the interior, however, where Maybach is likely to ditch a seven-seat layout for five or six captain's chairs.
Maybach is considered an important brand for Mercedes to develop, given the rising demand for luxury models, particularly in the SUV sector, with rivals such as Bentley and Land Rover finding notable success with the Bentayga and Range Rover.
Mercedes has also seen strong growth of its AMG performance arm and would like to emulate this success with Maybach on a smaller but still profitable scale.
The range-topping version of the new GLS, first reported to be on the cards by Autocar in 2016, is tipped to be priced above £120,000.
The model will build on initiatives taken with the two-year-old Mercedes-Maybach S-Class.
Mercedes-Maybach S600 review
Insiders involved in the development of the forthcoming SUV, known internally as the Maybach 9, say it will not only preview the look of the SUV, with a bold new grille among the key elements, but also highlight the kind of high-end features, including autonomous driving functions, due to be offered.
A high-level Mercedes official told Autocar: “We have been quietly surprised by the sales success of the Mercedes-Maybach S-Class, which is proving extremely popular in many key markets. The plan now is to extend the exclusivity surrounding the Maybach name into the upper end of the SUV segment. We’re confident that this new model will leave little to be desired in terms of luxury.”
The model, which is set to be called the GLS 560, is likely to be offered exclusively with the AMG-developed M177 twin-turbocharged 4.0-litre V8 petrol engine. In the S560, this produces 462bhp.