Reads like a typical Audi/VW/VAG-group excuse.
I think the truth is simply that the VAG-group is lagging behind others when it comes to applying hybrid technology in cars.
Can someone tell me exactly what kind of new technologies were demonstrated with the introduction of the Audi R8?
Afaik, the only 'new' thing there were the LED head lights.
With current battery technology, like the Li-Fe batteries you see more and more, it is clear that good/fast/functional hybrid can be created.
Many car makers already do this.
The fact that Audi doesn't use them is probably because their own technology in this area is still not entirely the production ready.
Where I live (Netherlands) VW/Audi/VAG is probably the biggest car seller in the country, with many models, nice lease-contracts and a big advertisement budget.
Yet, the VW Hybrid cars like the VW Jetta of Golf GTE are not that popular and haven't received very high marks. And this in a country where environmental cars benefit hugely from taks-shortcuts.
Besided all this is the fact that, again IMHO, ALL Audi performance cars suffer from obesitats. Even the all-aluminum Audi R8 is >3500 lbs. The RS4 and RS5 are even heavier. So complaining about the weight of hybrid cars is a case of nicely ignoring this same fact their own cars are not exactly lightweights either.