It will probably just stay the same as now. People will buy based on a perception of brand quality based on reliability, coupled with how the car looks on the inside and outside.
Fixed that for you.
Consumers are fickle.
- range - safety features - audio system - etc - acceleration
Will be more difficult for high-end brands (Range Roger, Porsche) to use as discerning factors if the "heart" of the vehicle is largely identical between a Kia and a Porsche.
Will luxury car makers go to the way of Vertu vs. iPhone, or Omega vs. Apple Watch?
In the car market, the “heart” has been the same for a long time. The Honda Accord has about as luxurious (at least 90%, you get leather, great driving sensors, strong V6, etc.) of any luxury sedan under 100k, but people still buy those. Those brands mean something to people.
The mental coping mechanism is also the fact that Honda/Toyota make a ridiculous amounts of civics/corollas/accords/camrys, so they have to have efficiencies of scale going for them more so than other company's line ups.