In the opinion of this network the Veyron was simply Volkswagen showing off producing a car for ridiculous excess as it has ridiculously excessive funds to spend on it. It is not the greatest supercar ever produced, not even close. It's fat and built around its looks instead of its looks being a product of its design. Gordon Murray (father of the McLaren F1) has a pretty good breakdown on the why the Veyron is overrated you definitely should read if you have not.
There are many areas Volkswagen can improve the Veyron beyond just raw acceleration. The proposed hybrid drivetrain is a great start. The McLaren P1 and Porsche 918 Spyder already show us hybrid high performance is not just the future but reality.
Volkswagen somewhat painted themselves into a corner with all their talk about the top speed of the Veyron which became its measuring stick. Now, they have to exceed that metric or the new car will be viewed as somewhat inferior. They really should focus on the weight of the hybrid drivetrain and the handling but wowing people with a 286 mile per hour top speed seems to be the goal.
This new Veyron will not arrive until 2016 if then. A Bugatti spokesperson stated, “Five developmental prototypes with differing powertrain combinations have been constructed up to now. They are based on the existing car but use various solutions that are being considered for the new model.”
As there are five different prototypes testing a lot can change. It is rumored that the W16 motor will be retained but clearly Bugatti is exploring their options. We can probably expect 1500+ horsepower and an absurd top speed though. We will have to see what happens.