I don't think is a good idea for Ferrari to invest in this car due to the cap on the budget they have.
since they can only spend a certain amount of money it will be wiser to save all the money they can for this car and start to already invest in the next car since they can put that money in this fiscal year.
Also true , but they need to have a car to secure 4th place in Championship because McLaren might bring them a surprise by the end of the season and if somehow Ferrari cannot keep 4th place...that will reduce the potential to develop the next a lot so that's why the still need to improve this car a bit not to fight with RedBull or Aston and Mercedes because clearly they cannot fight any of them ((. I'm a Ferrari fan and I can feel the pain of the race for them before it even starts;D