As others have pointed out, there are 5 Porsches coming to FH3 as Forzathon rewards alongside the 7 in the car pack. It’s nice to be able to get a few Porsches without having to drop any money after Porsche being an expansion in FM4, FH2, and FM6. Porsche cars are now appearing at launch for various upcoming racing games(GT Sport and Project Cars 2 to name a couple examples) as the EA deal expired and the upside of that is they should be included in the base game for FM7 and other future Forza games.
Some people have even pointed out that there are still some Porsches that can come in the remaining car packs and/or Forzathon challenges.