Soldato
Ref the lack of career mode - I honestly think that's something that may get added in later. With the current reduced amount of cars and tracks, it would be difficult to offer a career mode with enough variety, but that should be addressed over time.
I see no reason why they couldn't. I think the main focus post launch is going to be releasing cars/tracks for DLC. Kazunori Yamauchi has said he wants the final figure of cars to be close to the 500 mark. It wouldn't be difficult to add in new challenges or daily challenges like they did with GT6. A little something extra to keep people coming back for more.
Something I haven't mentioned and I've not seen anyone else mention yet is the speed of the UI. It's pretty damn snappy compared to previous releases. Though not as quick as GT6 I don't think to get in to races, it's no where near as slow as GT5 was. It sits comfortably in the middle. The addition of the Select button when doing the missions/challenges is a welcome change, so you can swap challenges on the fly now without the need to back out to the menu each time.