Ron, unless you were confusing Ducati for Harley, I wouldn't say the big dukes run out of breath. If they do, the same can be said for most engines as power drops off between peak and the rev limiter. A quick google search of dyno charts show the 1299s consistently drop off peak power about 500rpm before the cut out. My 1098 looks at tho it flat lines all the way to its 10750 rpm cut out. I've had it not much more than 260kmh and can't say its ever ran out of breath, but drag starts to take its toll from 260+ so 6th gear to the limiter may expose that.
I've spent a but of time on the latest Multistrada DVT with panniers and she pulls strong up to 220k. I didn't try a top speed run in 6th but there was no signs of running out of breath.
Ill take you up on the 1000cc BMW beating the Ducati on the road. Put simply you cant beat the effortless torque the big twins offer. For point to point speed the litre bikes need to be worked in comparison. Perhaps I'm spoilt spending the last five years on a 1098. Definitely have to rev the multis to achieve the same amount of pace up SH16 or over the para paras etc. it becomes tiresome if not in the mood.
How would the 1000cc manufacturers go at increasing the capacity by nearly 30% while retaining reliability, emissions same power per litre outpit?
A complete redesign? Bigger block, stronger, bigger internals?... issues with NVH due to the unbalanced nature of the I4? Just throwing ideas out there I'm no engineer and I don't have time to sit and read like I did when working 40 hour weeks but I don't think increasing capacity by 30% while retaining the attributes of the 1000cc engine is as easy as that.
I see where you're getting at with kw/litre. Can't say I agree on you opinion of the LS motors, and others not meeting a specific power per litre out put. IMO in the age of component sharing, fuel efficiency and guilt fuelled emission control, enjoy it while it lasts. Soon the 'performance' vehicle to have will be some wank factor double cab ute on 20 inch rims, sticker pack and some macho small cock syndrome sounding name.