Yes, the key is that all should be somewhat competitive. If a manufacturer is not competitive, it will just leave. Another reason why it's bad for the championship that Toyota is so dominant.
I don't think we'll ever see the 7 manufacturers from the early 2000's (even though Skoda, Hyundai and Mitsubishi WRC would see the podium through binoculars) until something drastic will change in a more or less far future, like a switch to electric.