Well it is a bit more complicated than that. Airbus did not suddenly change to an enhanced A320. The differences between a 1988 A320 and a 2010 A320 have been introduced over time. There was no sudden change (yet)
Yes the LCD screens and their new control panel are very visible, but new brakes, new FMS, engine updates etc have slowly trickled in.
You will see that yr company has to issue a news sheet with every new delivery showing the diff from the last aircarft.
The best way is to select the ser number when you go in the manuals every time, then you get the right info for the aircraft you are working on.