People giving Turn 10 a tad too much credit, I seriously doubt PD saw something about Forza 3 which caused GT5 to be delayed. I think it has to do with the crowd reaction when damage was revealed and also something Sony related ie Sony told them to hold it back for business reasons.
Garn Turismo is a lot like an RPG though and personally would not like to see Yamauchi wasting time making something other than GT. That is very selfish but nothing more I can say besides I like Gran Turismo games. If he does want to make RPG's I think it will be more of a case where Sony fund for another team to make RPG titles rather than having the current PD team make anything besides Gran Turismo.
Doubt they will humour him just because he made the GT franchise though, he will need to have a good idea before Sony fork out the money. Back to Gran Turismo, if you look at the PD website you will see the people in charge of PD are also in charge of the Playstation brand which shows how important the franchise is. It's a true system seller so Sony are happy for the game to take it's time so when it releases it sells systems. A good game can be delayed but a bad game? It will be bad forever. :P
