Allthough i find TDU 1 completely boring now i've done more then enough kms to justify this, GT4 lasted me about 3-5 months i play it now and then but TDU with its insane sized map will have a longer Duration of game play i don't really like the challenges and missions on the game i just like cruising and with the 2nd one having pretty much everything i wanted that 1st didn't have i should be set, not saying GT5 isn't awesome but its taken too long and the excitement has kinda disappeared.
They just spend too long making the next chapter, and by the time there about to realese it the gaming world has changed soo much they spend another 6-12 months fixing it to catch up.