That's right. A better option would be to have different studios retain the rights so you could get more movies overall, but just have them coordinate creatively so that they could be in continuity with each other.
Except that the bean-counters don't think that way historically. Rob Liefeld had an X-Men related project turned down in Mavel's comic division because they "were not in the business of generating IP for Fox studios".
If those rumors about a more congenial attitude are true, that might be changing, but I haven't seen enough for me to consider it confirmed yet.