Ducati is a V4, 90°, and power is in the order of 235-240 hp and max rpm around 16.5k. For the other top engines (Honda, V5, and Yamaha, 4 inline) there’s no big difference they are all in the same ballpark for both power and rpm (obviously some people will say Yamaha has lot less power than Honda etc, but it’s always a difference in the order of few hp, too small to be accurately evaluated by external viewers). Aprilia is a 3 in line and revs a bit lower and is also short on power at about 215-220 hp AFAIK. About Kawasaki (4 in line), Suzuki (V4) and Proton (V5) I know too little to say something of sure but in term of power they are probably in the same league as Aprilia.
As for the v8 concept,
http://www.22000rpm.com . After no one (unsurprisingly if you read what it’s written in the website...) supported the project for Motogp, there are rumours about the possibility that the engine will be used in a bike for 2005 World SuperBike, they said the same for 2004...