Your right, nothing is concrete and dates do change... but they never get any earlier. If a game date changes it will always be later.

Game are useless anyway. Head office print of those sheets to try and get people to pre-order games because they think they're coming out soon then they can mark that up as predicted sales and keep everyone happy.

I remember my local Game store having 6 "official" release dates for gran turismo 5 over the course of about 2 years.

Its all guesswork at the moment, as neither Microsoft or Sony has given a release date for their consoles.