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IMHO I think we will see Lean Burn technology for the next 10 years. The reason is because gasoline engines are developing very rapidly to meet the tight European 2020 CO2 regulation and LEVIII LD regulation from the California Air Resources Board (CARB). At this time Lean Burn and down sizing are being used to get us into the future.

A good example is the BlueDIRECT petrol engines from Mercedes-Benz

The BlueDIRECT petrol engines from Mercedes-Benz, which to date have comprised the familiar V6 and V8 engines, boast the very latest technology. A new addition is a six-cylinder engine which is being offered for the first time in the E-Class Coupé and Cabriolet not only as a naturally aspirated engine, but also as the E 400 with a displacement reduced to three litres but with a biturbo drive to compensate. With its power potential and formidable torque at low engine speeds, this six-cylinder model sets new standards in its segment. It produces 20 kW more power compared with the E 350. Its torque has increased by 110 Nm and is on tap between 1400 and 4000 rpm. On top of this, the new, efficient six-cylinder engine also fulfils the EU6 emissions standard. The E 500, meanwhile, not only promises sports-car-like performance – it is also making a name for itself as the most economical model in the V8 segment.

Another new addition to the BlueDIRECT petrol engine family is the four-cylinder petrol unit. With a combined fuel consumption in the E 250 Coupé of 5.7 litres and CO2 emissions of 132 grams per kilometre (Cabriolet 6.2 litres and 144 g CO2 per km) and producing 155 kW (211 hp) from a displacement of just two litres, plus 350 Nm of torque across a wide range from 1200 to 4000 rpm, it redefines standards in the four-cylinder segment. Producing a 0 to 100 km/h acceleration time of 7.1 s (Cabriolet 7.5 s), it really underlines the sporty temperament of the Mercedes-Benz E-Class Coupé and Cabriolet.

Lean-burn process with stratified charge operation

Depending on the operating conditions, the new four-cylinder engine operates in stratified charge or homogenous mode. With stratified charge operation, the high-compression engine runs with significant excess air. To achieve this, the fuel is only sprayed into the air, which has already been compressed by the pistons, during the compression phase. A precisely controlled electronic multiple injection system helps to ensure that a fuel/air cloud builds up in a limited area around the spark plug, precisely at the time of ignition. The spark plug lights the ignitable fuel/air mixture around it, while only a very lean mixture with a high proportion of excess air is to be found in the remainder of the combustion chamber. This enables extremely efficient combustion.

A prerequisite for stratified charge operation is fast piezo injectors. They spray the fuel into the combustion chambers several times in succession per power stroke, and as such enable specific control of the mixture formation and thus the flammability.

The new four-cylinder petrol engine from Mercedes-Benz also sees the world’s first use of this stratified lean-burn process in combination with exhaust-gas turbocharging and external high-pressure exhaust gas recirculation. As a result, the E 250 Coupé is the only vehicle in this segment to achieve efficiency class A. In addition, the new BlueDIRECT four-cylinder petrol engines already meet the EU6 emissions standard which will apply from 2015. The new four-cylinder unit also meets the EU6 emissions standard in the guise of the homogenous variant for countries with different fuel qualities.

Source 2014 Mercedes-Benz E Class Cabriolet | Sense The Car

With Lean burn engines they will have lean NOx control (lean deNOx) technologies.