I'm sure many of you have been wondering, but why exactly has GT5 taken so long to develop?
(credit to Fredzy from GTplanet)
A: [Laughs] Well, with developers like Yamauchi-san, it may look from the outside that they spend as much time as they want, but they really do work hard to get the game done. They wish that they could release these games more frequently. But because of the pressure they put on themselves, they have been doing the best they can.
It's true that it has been five years since the last true game - Gran Turismo 4 - was released; when you look at it like that the team seems to be taking forever. But Gran Turismo is one of the faces of the Playstation brand, so they always get requests from the platform side to make technical demonstrations. Kazunori would remind you that, from Polyphony's standpoint, they have released something almost every year, like Gran Turismo HD, the one-track demo or Gran Turismo Proto or the PSP Gran Turismo. So, yes, they aren't like other developers that can release games year after year, but they are also in the situation that they have additional responsibilities to the platform. So I'm half-agreeing with your statement, but also trying to explain the situation around Gran Turismo.
It seems they simply have a lot on their plate, being forced to work on 2-3 full projects simultaneously while also working on various demos and whatnot (like the 3D demos from last year) to show off SCE's latest technology.
Of course, there's also the fact that both GT5 and GT PSP have the content of 3-4 full games. More like 20 games, if you compare them to something like MotorStorm. 
Also, according ro Famine over at GTPlanet, the GT Academy is coming to North America:
From the way it sounds over at GTP, it'll be arriving here alongside GT5's release. It's as if they're trying to make the Gran Turismo as big in North America as it is in Europe.
The current GT Academy finals are actually going on right now (credit to solidsnakex on neogaf). All contestants recieved a full racing suit.
Also, for all those who missed it (most people did - it got very few posts), check out my other thread covering screenshots of the online interface for GT5.
And finally, here are some new screens:
Essay Pro