As much as we'd like to see an A6 Avant here in the United States, though, we wouldn't get our hopes up. Sure, the Mercedes-Benz E-Class is still available in regular-old wagon form, but you have to special order a Volvo V90 and well, that's it. There's just not much demand for luxury wagons like the Avant.
Ah, but there's hope! The A6 spawned one of the first off-roadish luxury wagons back in 2001 and there's presently an Audi A6 Allroad sold in Europe. Given the V90 Cross Country, the Mercedes E-Class All-Terrain and the A4 Allroad, it's not that far fetched to imagine a new A6 Allroad coming here. In fact, it seems like a good bet.
In any event, expect the 2019 A6 to be on par with the mechanically related and recently introduced A7. The interior will be more spacious and perhaps not as radically designed, but the immense amount of technology should be the same - including Audi's new dual-touchscreen infotainment system and Virtual Cockpit (see video below). The A7's new turbocharged 3.0-liter V6 (complete with 48-volt mild hybrid system) seems likely as well, but like the current A6, a base 2.0-liter turbo engine is likely.
Given how far along these prototypes are, it seems likely that we'll see the camouflage come off very soon.