I don't think he means fail financially or by lack of sales, but by actual quality and gameplay.

I wouldn't worry--P.D. knows what they're doing.  It will look beautiful and drive VERY realistically.

As others have said, you have to define what you mean by failure. From a sales perspective, it will sell a huge number of copies... but it might be behind previous games in the series for total sales figures. Would that make it a failure?

From a gameplay standpoint, a lot of people have been happy with Gran Turismo as it is and they're only adding good things to the existing formula. But it might not have a feature or two that a competing game has. Would that make it a failure?

I would answer no to both of those questions and I'm convinced that GT5 will be a success on both fronts, even if it's not an overwhelming, blow everyone away success.

From a sales perspective = not a fail. GT 5 should sell a minimum of 8 million sales ltd. Maximum is anyone's guess.

From a review perspective = not a fail. High 80s to Low 90s on metacritic.

From a racing game fan's perspective = not a fail. Best racing car game ever made.

From a non-racing game fan's perspective = Fail!!! Racing games do not fully capture the real life experience of driving a car. Racing games are dull and boring.

a dev lik ePD and a perfectionist like Yamauchi that have delivered again and again must be doing something good by talking so much.

PPD Is making sure GT5 is done before they release it will be 100% full of win unlike GT2.
GT 2 98.6% = Fail
Anyone remember that "bug"?
"Wow its a F**king drag car, Cooooool, hmm but where to race it?"

Its probably going to sell 12M+ if its the only GT game released this generation. They only really need one, why make two when that'll just cut short the sales of the first and perhaps they'll even be able to make launch ZOMG!!