The V-Rod engine was designed for a lighter bike and for people who would normally be customers of the sportier Japanese brands that ran at higher rpm. The existing engine would not have been a good match for a nearly 1000 pound Touring rig, where good low end torque is more important than high rpm power. That's not to say they couldn't have increased displacement, up to a point, and gone with a torque cam and tune. But it still wouldn't look or sound like what the majority of Harley customers wanted, and I assume that's why they never tried that approach. With new sportier models on the drawing boards, perhaps there will be something they can use the Revolution engine in. However, that engine wasn't cheap to make, and odds are they will find a less expensive option for the new bikes they plan to bring to market.
JMHO - Jerry