The Gallardo is technically near 9 years old, which is about the age Lamborghini starts to phase out its cars. In fact, that's the same age as the Murcielago.
Even with the LP560-4 refresh, it's still on the edge of 4 years (again, the same "age" as the LP640 before it was ceased) & Lamborghini has exhausted it with all the special editions.
To be quite blunt, the Gallardo replacement is already supposedly in the works under the name Cabrera. And as the rumors go, it will be unveiled in 2012 & put into production in 2013, which actually corresponds well with Lamborghini's production timeline.