If I had to guess as to what vehicles the Gen 3 platform would support, it would be:
1) Dedicated RoboTaxi.
2) Compact consumer sedan (the 25K Tesla).
3) A hatchback version of #2 above (mainly for the Euro market).
Each of these models would be on the same skateboard and have identical substructures, only the bodies would be slightly different from each other. Designed with economical & very high volume manufacturing in mind.