The Q4 is really looking like a less practical version of the Q3 for the time being. Given that the 2019 Q3 already has a sloped rear window, this one is shaping up to be an even more severe slant. Most of the headlights and taillights are uncovered on the camouflaged car, and both units look a lot like the Q3 lights. It's probably all part of the disguise, but Audi chose to use a honeycomb grille for this Q4 test mule. That design detail is typically saved for the high performance RS trim Audis nowadays.
Audi is playing catchup in this segment at the moment. Both BMW and Mercedes have entries with the X2 and GLA and GLC, which seem to be doing just fine. This continues to be the case in the coupe SUV world of Audi, as it just recently launched the Q8 flagship SUV.
We will fully expect this car to ride on Volkswagen's MQB architecture, just like the Q3. The engine will almost surely be the same 2.0-liter turbocharged four-cylinder as in the 2019 Audi Q3 we recently drove. This means either 184 horsepower or 228 horsepower, depending on the trim level. It wouldn't be a surprise to see the higher power option be the standard engine on what's bound to be the more expensive Q4. The eight-speed ZF transmission is always a good guess for what will be doing the shifting.
Audi is apparently prepping a new RS Q3 that could make it stateside too. An RS Q4 wouldn't be out of the question, but we don't imagine this is it, despite the grille. The Q4 will likely be revealed late in 2019 as a 2020 model year.