When GT5 has as much to do in it as GT4 did, I'll consider it finished. The thing is, finished or not doesn't really matter because they're still working on it, if they'd released it in the state it was at launch and never updated it then yeah, it would be a problem. Although the lack of events is inexcusable next to GT4's massive list of stuff to do, at least PD recognised that and add a new race event and a pair of time and drift trials at least twice a month, often 4 times a month, very occasionally more than that, sometimes less, and they have genuinely worked to fix the problems people were having.
Ok, so not all their efforts hit the mark, but Spec II has rekindled my faith in PD and GT5, they DO listen after all. They're just a bit slow, maybe stubborn and (until recently) uncommunicative.
Still, for me it needs more A-Spec to keep me busy, an online drag race mode (I wouldn't use it, but it would keep idiots out of free track/drift lobbies), the ability to give everyone the same STANDARD car (if that hasn't already been added, I haven't checked) and a whole load more premiums from 2009-2012 (model year) before I'll consider it finished, but I'm more than happy to wait.