Though I don't know about any revenue sharing, assuming it's there and that Google would take it away, would it incentivise faster updates? Definitely. Would it actually produce faster updates? Very much doubt it.
At least for OnePlus it wasn't a lack of willingness, prioritisation, or ability. Both the Cyanogen team and the Paranoid Android team, which got hired later on, are highly skilled and have a lot of experience.
Most of the time was spent integrating drivers from external providers such as Qualcomm and JDI. A lot of the time we were simply waiting for working drivers for the hardware we were using and other times we were waiting on bug fixes.
For the biggest OEMs such as Samsung this might actually help them prioritise as they have a more customised OS and as such might spend more time there. Though I'd wager a guess that the reason they cannot move faster is also due to waiting on 3rd party companies not affected by this ad-sharing penalty and that they have a hard time hiring qualified people who know the android system well enough to move things faster.
IIRC the Galaxy Nexus for example was abandoned because TI left the mobile business and could not provide new drivers.
I purchased a note 4 because I had a decent experience with the note 2 but after waiting almost an entire year for lollipop I was dissipointed that they didn't rip out TouchWiz and ship a vanilla android ROM with apps. I'd give Kindle Fires and the Fire Phone the same criticism.
The only thing currently keeping me on the standard ROM is the Samsung Camera app which is second to none. Unless someone can correct me and earn internet karma.