A down-sized version of GM's popular 2.7-liter gasoline engine in works

The lineup currently has a range of gasoline engines

The automaker has broadly four types of four-cylinder gasoline engines in this series, starting with a 1.3-liter (L3T), 2.0-liter (LSY), and various iterations of its 2.7-liter block. The former is offered with Chevy Trailblazer, while the latter can be seen in Cadillac CT4, CT5, XT4, XT5,  XT6, Chevy Blazer, and GMC Acadia.

The 2.7-liter L3B engine from GM comes in two variations: one for Cadillac and one for trucks (Chevy Silverado 1500/GMC Sierra 1500). The truck engine is startlingly powerful for a sub-3.0-liter four-cylinder engine, producing 310 horsepower and 430 pound-feet of torque. It produces 325 horsepower and 380 pound-feet of torque in the Cadillac CT4-V. Although the new 2.5-liter engine's estimated power output is unknown at this time, 300 horsepower and 350–400 pound-feet of torque don't seem improbable. A less expensive L3B variation known as the L2R engine, which produces 237 horsepower and 260 pound-feet of torque, also exists in the CCS lineup. 

A down-sized version of the 2.7-liter block

The new motor is likely to be a scaled-down L3B engine. That indicates it will be an inline-four made entirely of aluminum with a single turbo and dual overhead cams (DOHC). Reports reveal that the motor will be tuned to produce a healthy torque figure while providing better fuel efficiency.

It is unclear if the new 2.5-liter iteration is intended to replace the current 2.7-liter L3B engines in the lineup. There is also a possibility that it may replace either one - Truck or the Cadillac version. GM may also add the product to its lineup, letting it co-exist with other variants. 

It is expected that news regarding the development will officially surface by the end of the year.