bmer

Personally I think Audi should drop the FWD from A5 models. The A5 is quite expensive here as it starts at 46,450 euros (1.8 TFSI) and most of the models cost more than 60,000 euros. For that kind of money I think many people expect the car to have quattro as it is one of the most important things Audi is known for.
I also think this is a price class where vast majority of the ordered cars are loaded with options so there isn't really much need for low equipment level models.
Coupes are usually considered to be sportier than their 4-door siblings so it makes more sense to offer FWD in the A4 than in the A5. Furthermore, A5's main competitors (3er Coupe & CLK) are both RWD so you could say Audi is giving them some advantage by not offering quattro as standard. The 3.2 FSI is at the higher end of A5 range and with FWD it can't compete with a E92 powered by a comparable engine. And like I said, money is hardly big an issue in this price class so why keep offering FWD with this engine?

I recall that the 1.8T in the B6/B7 A4 was propably the most popular engine choice (at least where I live) and most of them were ordered with quattro so there is likely to be a similar demand for a 4WD low-end model (A5 1.8 TFSI quattro) especially because it's not that much more expensive.