I can see this agument from all angles, you have many lfs fans who paid there money for the game which is now going a little stale and want some new content then you have the guys developing it who want to make it perfect before they release it which is all well and good and the correct approach(GT5 springs to mind).
I think what would have stopped all this would have been for the developers not to have announced the scirroco or rockingham in 2008 to be still working on it by the end of 2010 with few updates on progress in this way people wouldnt be getting tired of waiting so long but to be fair 1 car and 1 track will not make that much difference in the grand scheme of things they will quickly become the norm and then we will be back to square one wanting more new tracks and cars.
Im sure opinions differ greatly but maybe in the future things that are only on the drawing board will not be announced until they are close to fruition.