I have to say thought that the amount of cars is relevant for the GT5 case because of the number of tracks and the cars feature on the series,if you think about it the can do 350 to 450 premiums but is unnecessary because most of the cars of GT4 will be lost,and the amount of different models,badges and cars will be less.
I know the repetitive car thing but they don't sum more that 75 variations of the same cars which will sum in total an amount of 800 to 900 different models to choose from(GT has more than 1000 cars BTW),and since the amount of tracks is really huge is necessary a good amount of cars.
Besides of that lets face the fact that 140 employees cannot do 1000 premium cars in a period of 5 years,it will be like 10 to 30 cars per employee in a year,and each car will the full reproduce cockpit,engine sound,scripting and so on,but as we know they are not 140 modellers,they have to take part in different parts of the production and that includes tracks,B-spec mode,track creator,UI and so on.
Its not worth to change 10 to 15 cars for a super quality model,it eventually will lead to a huge decrease of car selection and game enjoyment,I have analyse the fact that they could do 450 premiums and get in the same numbers with forza but at the end those excluded cars will be lost and some of them will not appear,I do mean it because one of the strengths of GT games is the car selection.
some people may not like b-spect,weather and day/night transitions but if you do think about it 1000 cars,200 premium models,what else do you want?.
And more important is it really possible with their resources?
the answer to that is simple yet will be reject by everyone: NO,you may not have an idea how 60million can be expended on software development over 5 years,its 1.2 million per year,100.000 at month and 33.000 at day so you have to think about the payment for the employees,the copyrights and licensing,also the physical machinery(huge scanners and computers capable of rendering at those resolutions)and some trips to the actual tracks
You may find that all its there and for a game with this characteristics you will need a well experienced crew of 200 to 250 employees,over the same time of development and so on...
I have gone a bit of topic but finally to me:
+cars=+fun
lim_cars=lim_fun